synthesis and characterization of biofunctionalized

SYNTHESIS AND CHARACTERIZATION OF

BIOFUNCTIONALIZED POLYURETHANES

By

Kashif Mahmood

2010-GCUF-6890-228

Thesis submitted in partial fulfillment of the requirements for the degree of

DOCTORATE OF PHILOSOPHY

IN

APPLIED CHEMISTRY

DEPARTMENT OF APPLIED CHEMISTRY

GOVERNMENT COLLEGE UNIVERSITY, FAISALABAD.

2017

DEDICATED

TO

My Loving Parents, FAMILY MEMBERS &

Dearest Sons

Muhammad Abubakar & Muhammad

Umar

CONTENTS

NO. Title Page no.

I Acknowledgement i

II List of abbreviations ii

III List of Tables iv

IV List of Figures vi

V List of Schemes ix

VI Abstract x

CHAPTER 1 INTRODUCTION 1-14

1.1 Polymer 1

1.2 Polyurethane 1

1.2.1 Chemistry of polyurethane (PU) 2

1.2.2 Raw materials for PU synthesis 2

1.2.2.1 Isocyanate 3

1.2.2.2 Polyols 5

1.2.2.3 Chain extenders 6

1.2.3 Preparation of polyurethane 7

1.2.4 Kinds of PU and its uses 8

1.2.4.1 Soft PU foam 8

1.2.4.2 Stiff PU foam 8

1.2.4.3 Coating, Adhesive, Sealants and Elastomers (CASE) 8

1.2.4.4 Thermoplastic polyurethane (TPU) 9

1.2.4.5 Waterborne polyurethane dispersions (PUDs) 9

1.2.4.6 Apparel and appliances 9

1.2.4.7 Automotive and electronics 10

1.2.4.8 Flooring and furnishings 10

1.3 Bio-functionalized PU Materials 11

1.4 Chitin 11

1.5 Curcumin 12

1.6 Clay 13

1.7 Amis and Objectives 14

CHAPTER 2 REVIEW OF LITERATURE 15-38

2.1 Polyurethane and polyurethane based materials 15

2.2 Curcumin and curcumin based materials 17

2.2.1 Biomedical uses of curcumin and its blended substances 18

2.2.1.1 Nano-technique curcumin has therapist properties 19

2.2.1.2 Curcumin and resveratrol encapsulation 19

2.2.1.3 Curcumin stimulated wound covering 20

2.2.1.4 Curcumin derivative applied against diabetic problems 21

2.2.1.5 Curcumin behave as antibacterial materials 21

2.2.1.6 Neuroprotective achievement 22

2.2.1.7 Anti-cancer action of curcumin based nano-materials 22

2.2.1.8 Efficacy of curcumin in the covering of paracentesis in rats 22

2.2.1.9 Curcumin applied in the finding of HCIO 23

2.3 Chitosan/chitin based materials 24

2.4 Chitosan/curcumin based materials 26

2.4.1 Chemical interaction between curcumin and chitosan 26

2.4.2 Preparation of CUR-CHI nanoplex 27

2.4.3 CUR carrying CHI schemes and their potential behaviors 28

2.4.4 Polysaccharide/curcumin-chitosan nano-technique 29

2.4.5 Protein/curcumin-chitosan nanosuspension 32

2.4.6 O-carboxymethyl CHI nanocarrier for curcumin 33

2.4.7 Amphiphilic-chitosan microparticles and curcumin 34

2.4.8 Metal Oxide-chitosan nanocomposite for curcumin delivery 35

2.5 Clay based polymer bio-nanocomposites 36

CHAPTER 3 MATERIALS AND METHODS 39-70

3.1 Chemicals/apparatus 40

3.1.1 Chemicals 40

3.1.2 Apparatus 40

3.2 Synthesis of novel curcumin based polyurethanes varying

diisocyanate structure

41

3.2.1 Synthesis of polyurethane 41

3.3 Synthesis of chitin / curcumin / BDO / clay blends based

polyurethane elastomers and bio-nanocomposites

46

3.3.1 Preparation of polyurethane elastomers and bio-nanocomposites 46

3.4 Characterization 66

3.4.1 Structural/morphological characterization 66

3.4.1.1 Fourier transforms infrared (FT-IR) spectroscopy 66

3.4.1.2 Solid state NMR 66

3.4.1.3 Scanning electron microscope (SEM) 66

3.4.2 X-ray diffractometry (XRD) 67

3.4.3 Thermal Analysis 68

3.4.3.1 Differential scanning calorimetry (DSC) 68

3.4.3.2 Thermogravimetric analysis (TGA) 69

3.4.4 Antimicrobial activity test 69

3.4.5 Surface characteristics 70

3.4.5.1 Evaluation of water absorption 70

3.4.5.2

3.4.6

Equilibrium degree of swelling

Statistical analysis

70

70

CHAPTER 4 RESULTS AND DISCUSSION 71-179

PART-I

4.1 Molecular and biological characterization of novel curcumin

based polyurethanes varying diisocyanates

71

4.1.1 Molecular characterization 71

4.1.2 Scanning electron microscope (SEM) analysis 77

4.1.3 Biological activity analysis 79

4.1.3.1 Antimicrobial and antifungal activity 79

PART-II

4.2 Molecular, thermal and surface characterization of

chitin/curcumin/BDO blends based polyurethanes

82


4.2.2 Solid state proton nuclear magnetic resonance spectroscopy (SS

1HNMR) analysis

86

4.2.3 Scanning electron microscopy (SEM) analysis 91

4.2.4 X-Ray Diffraction analysis 93

4.2.5 Thermal characteristics 95

4.2.5.1 Thermogravimetric (TGA) analysis 95

4.2.5.2 Differential scanning calorimetery (DSC) 97


4.2.6.1 Assessment of water absorption percent (%) and equilibrium

degree of swelling

99

PART-III


curcumin/BDO blends based polyurethanes

102


4.3.2 Solid state proton nuclear magnetic resonance spectroscopy (SS

1HNMR) analysis

104


4.3.4 X-Ray Diffraction Studies 107


4.3.5.1 Thermogravimetric (TGA) study 109




degree of swelling

113

PART-IV


curcumin/chitin blends based polyurethanes

115


4.4.2 Solid state proton nuclear magnetic resonance spectroscopy

(SS1HNMR) studies

117








degree of swelling

126

PART-V

4.5 Molecular, thermal and surface characterization of chitin-clay /

curcumin-clay / BDO-clay blends based polyurethane elastomers

128

and bio-nanocomposites









degree of swelling

138

PART-VI


chitin/curcumin/BDO/clay blends based polyurethane bio-

nanocomposites

141




4.6.4 Thermal analysis 147





degree of swelling

151

PART-VII


curcumin/BDO/clay blends based polyurethanes

154



4.7.3 X-Ray Diffraction Studies 158






degree of swelling

164

PART-VIII


chitin/curcumin/clay blends based polyurethanes

167









degree of swelling

177

CHAPTER 5 SUMMARY 180

6 REFRENCES 183-201

7 APPENDICES 202

i

ACKNOWLEDGEMENT

All praise to Almighty Allah, the most merciful and the compassionate of the universe who

gave me potential and ability to complete this research work successfully. I offer my

humblest words of thanks to Holy Prophet Muhammad (SAW), a torch of guidance and

knowledge for humanity.

I feel great pleasure in expressing my sincerest gratitude and paying rich tribute to my

illustrious and dedicated supervisor Dr. Khalid Mahmood Zia (Director ORIC / Associate

Professor, Department of Applied Chemistry, G.C University, Faisalabad) for tremendous

cooperation, valuable suggestions and noble guidance, enabled me to complete my research

work.

I am thankful to Prof. Dr. Muhammad Zuber for providing necessary research facilities. I

would like to express thanks to Dr. Tahsin Gulzar Chairman, Department of Applied

Chemistry, regarding helpful support on this research. I would like to express my deep

gratitude to Dr. Shazia Tabasum, Dr. Saima Rehman, Dr. Nadia Akram, Aqdas Noreen

and Fatima Zia regarding helpful and technical discussions on certain aspects of this

research.

I sincerely thank to my loving parents for their love and wish to see me glittering high on the

sky of success. I ought to acknowledge the encouragement, prayers and support to me. I am

nothing without their moral and financial support; the present distinction would have merely

been a dream. They always acted as a light house for me in the dark oceans of the life path.

No words can really express the feeling that I have for my beloved parents. I‟m very

appreciative to my wife Kalsoom Akhtar and Sons; Muhammad Abubakar &

Muhammad Umar who have much suffered during this doctoral study but she was always

encouraging during my study.

Kashif Mahmood

2010–GCUF-6890-228

ii

LIST OF ABBEREVIATIONS

AMPK AMPkinase

AR Aldose reductase

BDO 1, 4-butane diol

CASE Coating, Adhesive, Sealants and Elastomers

CD Cyclodextrins

CHI Chitosan

CUR Curcumin

DCE Degradable chain Extender

DMPA Dimethylol propionic acid

DMSO Dimethyl sulfoxide

DMT Dimethyl terephthalate

DPPC:CHOL Dipalmitoylphosphatidylcholine:cholesterol

DSC Differential scanning calorimetry

FE-SEM Field-emission scanning electron microscope

FT-IR Fourier Transform Infra-Red Spectroscopy

GL Gelatin

H12MDI 4,4-Dicyclohexylmethane diisocyanate

HA Hexosamine

HA Hyaluronic acid

HAD hexa-1,6-diamine

HMDI Hexamethylene diisocynate

HTPB Hydroxy terminated polybutadiene

IPDI Isophorone diisocyanate

LbL layer-by-layer

MDI Diphenylmethane diisocyanate

MMT Montmorillonite

MPO Myeloperoxidase

NCs Nanocomposites

NDI Naphthalene-1, 5-diisocyanate

NGs Nanogels

NTPU NCO terminated polyurethane prepolymers

n-ZnO Nanostructured zinc oxide

o-CMCS o-carboxymethyl chitosan

iii

OSB Oriented Strand Board

PCL Polycaprolactone diols

PEA Polyethylene Adipate

PEG Poly(ethylene glycol)

PET Poly(ethylene terephthalate)

PI-βAA Poly(isoprene-β-acrylic acid)

PIR Polyisocyanurate

PPF Polyurethane packaging foam

PTMA Polytetramethylene Adipate

PTMEG Polytetramethylene ether glycol

PU Polyurethane

PUBNC Polyurethane bio-nanocomposites

PUD Polyurethane dispersions

PUDs Waterborne polyurethane dispersions

PUEs Polyurethane elastomers

RIM Reaction injection molding

ROS Reactive oxygen species

SDS Sodium dodecyl sulfate

SEM Scanning electron microscopy technique

SP Smart Polymers

SS1HNMR Solid state proton nuclear magnetic resonance

spectroscopy

TDI 2, 4-toluene diisocyanate

TEA Triethylamine

TGA Thermogravimetric analysis

TPU Thermoplastic polyurethane

VOC Volatile Organic compound

XRD X-ray diffractometry

iv

LIST OF TABLES

Table Title

Page

1.1 Raw constituents use for PU preparation 3

1.2 Chemical structures of diisocyanates 4

3.1 Formulation ratio of different raw materials used in the synthesis of

polyurethanes extended with blends of curcumin/1,4-butane diol

45

3.2 Sample code designation and various constitutions of BDO/curcumin/chitin

established polyurethane elastomers

51

3.3 Sample code designation and different formulation of BDO/curcumin based

polyurethane elastomers

53

3.4 Sample code designation and different formulation of curcumin/chitin based

polyurethanes

55

3.5 Sample code designation and different formulation of BDO / curcumin /

chitin / clay based polyurethane elastomers and bio-nanocomposites

59

3.6 Sample code designation and different formulation of BDO / curcumin /

chitin / clay based polyurethane elastomers and bio-nanocomposites

61

3.7 Sample code designation and different formulation of BDO/curcumin/clay

based polyurethane elastomers and bio-nanocomposites

63

3.8 Sample code designation and different formulation of curcumin/chitin/clay

based polyurethane elastomers and bio-nanocomposites

65

4.1 Antibacterial activity of the curcumin based polyurethanes 80

4.2 Antifungal activity of the curcumin based polyurethanes 81

4.3 Water absorption (%) of chitin/curcumin/BDO based polyurethane samples 100

4.4 Swelling action of chitin/curcumin/BDO based polyurethane samples 101

4.5 Water absorption (%) of BDO/curcumin based polyurethane samples 113

4.6 Swelling behavior of BDO/curcumin based polyurethane samples 114

4.7 Water absorption (%) of chitin/curcumin based polyurethane samples 126

4.8 Swelling behavior of chitin/curcumin based polyurethane samples 127

4.9 Water absorption (%) of chitin/curcumin/BDO/clay based polyurethane

samples

139

4.10 Swelling actions of chitin/curcumin/BDO/clay based polyurethane samples 140

4.11 Water absorption (%) of BDO/chitin/curcumin/clay based polyurethane

samples

152

4.12 Swelling behavior of BDO/chitin/curcumin/clay based polyurethane samples 153

v

4.13 Water absorption (%) of BDO/curcumin/clay based polyurethane samples 165

4.14 Swelling behavior of BDO/curcumin/clay based polyurethane samples 166

4.15 Water absorption (%) of chitin/curcumin/clay based polyurethane samples 178

4.16 Swelling behavior of chitin/curcumin/clay based polyurethane samples 179

vi

LIST OF FIGURES

Figure

Title Page

1.1 Structure of PU 2

1.2 Structure of chitin 12

1.3 Structure of curcumin 13

2.1 Schematic representation for the formation of hollow nanocapsules via

electrostatic layer-by-layer (LbL) self-assembly, drug loading and release

20

2.2 Proposed mechanism of the recognition of hypochlorous acid using

curcumin

24

2.3 Hydrogen bonding interactions between curcumin and chitosan molecules 27

2.4 Preparation of amorphous curcumin–chitosan nanoparticle complex (or

nanoplex in short) via the drug–polysaccharide complexation method that

involved the mixing of curcumin (CUR) solution in base with chitosan (CHI)

solution in acid

28

2.5 Proposed scheme illustrates the presence of the solubilized and unsolubilized

curcumin in the chitin sheet in a phosphate buffer solution (pH 7.4) at 37 ºC

30

2.6 Chemical structure of (A) O-CMC, (B) curcumin; (C) Solubility of curcumin

(a) curcumin in water, O-CMC Nps and curcumin-OCMC Nps

34

2.7 Pictorial representation for O-CMCS/n-ZnO nanocomposites (i) and O-

CMCS/n-ZnO/curcumin nanocomposite

36

3.1 Scanning electron microscopy technique 67

4.1 FTIR spectra of monomers: (a) hydroxyl terminated polybutadiene (HTPB),

(b) hexamethylene diisocyanate (HMDI), (c) 1,4-butane diol (BDO), (d)

curcumin and (e) chitin

73

4.2 FTIR spectra of various diisocyanates (a) HMDI; (b) IPDI; (c) H12MDI; (d)

TDI; (e) MDI

75

4.3 FTIR spectra of polyurethane extended with blends of curcumin and 1,4-

butane diol (IPU3)

76

4.4 SEM images of blends of curcumin and 1,4-butane diol extended

polyurethanes (IPU 1-IPU 5)

78

4.5 FTIR spectra of polyurethane prepolymer and final polyurethane to confirm

the PU formation: (a) PU prepolymer, (b) BDO based polyurethane, (c)

curcumin based polyurethane and (d) chitin based polyurethane

83

4.6 FTIR spectra of polyurethane prepolymer and final polyurethane to endorse

the planned PU structure: (a) PU prepolymer, (b)

BDO(50%)/curcumin(25%)/chitin(25%) based polyurethane, (c)

BDO(25%)/curcumin(50%)/chitin(25%) based polyurethane and (d)

BDO(25%)/curcumin(25%)/chitin(50%) based polyurethane

85

4.7 Solid state 1H NMR spectrum of BDO based PU (KPU1) 87

4.8 Solid state 1H NMR spectrum of curcumin based PU (KPU2)

88

vii

4.9 Solid state 1H NMR spectrum of chitin based PU (KPU3)

89

4.10 Solid state 1H NMR spectrum of curcumin/chitin/BDO blends based PU

(KPU6)

90

4.11 The SEM images of pristine and blends of chitin, curcumin and BDO based

PUs, KPU1-KPU6

92

4.12 The X-ray diffractograms of pristine and blends of chitin, curcumin and

BDO based PUs, KPU1-KPU6

94

4.13 The TGA curves of polyurethane samples (KPU1-KPU6) 96

4.14 Differential scanning calorimetery (DSC) curves of samples KPU1-KPU6 98

4.15 The FTIR spectra of PU prepolymer and final PU to confirms the proposed

polyurethane structure: (a) PU prepolymer, (b) BDO(75%)/curcumin(25%)

based polyurethane, (c) BDO(50%)/curcumin(50%) based polyurethane and

(d) BDO(25%)/curcumin(75%) based polyurethane

103

4.16 Solid state 1H NMR spectrum of BDO/curcumin blends based PU (KPU8) 104

4.17 The SEM images of pristine and blends of curcumin and 1,4-butane diol

based polyurethanes (KPU1,KPU2) and (KPU7-KPU9)

106

4.18 The X-ray diffractograms of pristine and blends of curcumin and BDO based

PUs, (KPU1, KPU2) and (KPU7-KPU9)

108

4.19 The TGA curves of polyurethane samples (KPU1,KPU2) and (KPU7-KPU8) 110

4.20 The DSC curves of polyurethane samples (KPU1,KPU2) and (KPU7-KPU9) 112

4.21 The FTIR spectra of PU prepolymer and final PU to confirms the proposed

polyurethane structure: (a) PU prepolymer, (b) curcumin(75%)/chitin(25%)

based polyurethane, (c) curcumin(50%)/chitin(50%) based polyurethane and

(d) curcumin(25%)/chitin(75%) based polyurethane

116

4.22 Solid state 1H NMR spectrum of curcumin/chitin blends based PU (KPU11) 117

4.23 The SEM images of pristine and blends of chitin and curcumin based

polyurethanes, (KPU2, KPU3) and (KPU10-KPU12)

119

4.24 The X-ray diffractograms of pristine and blends of curcumin and chitin

based PUs, (KPU2, KPU3)) and (KPU10-KPU12)

121

4.25 The TGA curves of polyurethane samples (KPU2, KPU3) & (KPU10-

KPU12)

123

4.26 The DSC curves of polyurethane samples (KPU2,KPU3) and (KPU10-

KPU12)

125

4.27 The FTIR spectra of PU prepolymer and final PU to confirm the proposed

polyurethane structure: (a) PU prepolymer, (b) 1,4-butane diol/clay(0.1%)

based polyurethane, (c) curcumin/clay(0.1%) based polyurethane and (d)

chitin/clay(0.1%) based polyurethane

129

4.28 The SEM images of chitin, curcumin and BDO based polyurethane,

elastomers (KPU1-KPU3) and bionanocomposites (KPU1/clay-KPU3/clay)

131

4.29 The X-ray diffractograms of pristine curcumin, chitin and BDO based PUs,

(KPU1-KPU3) and curcumin, chitin, BDO and clay based PU

bionanocomposites (KPU1/clay-KPU3/clay)

133

4.30 The TGA curves of polyurethane samples (KPU1/clay-KPU3/clay) and 135

viii

(KPU1-KPU3)

4.31 The DSC curves of polyurethane samples (KPU1/clay-KPU3/clay) and

(KPU1-KPU3)

137


polyurethane structures: (a) PU prepolymer, (b)

BDO(50%)/curcumin(25%)/chitin(25%)/clay(0.1%) based polyurethane, (c)

BDO(25%)/curcumin(50%)/chitin(25%)/clay(0.1%) based polyurethane and

(d) BDO(25%)/curcumin(25%)/chitin(50%)/clay(0.1%) based polyurethane

142

4.33 The SEM images of blends of chitin, curcumin, BDO and clay based

polyurethanes (KPU4-KPU6) and (KPU4/clay-KPU6/clay)

144

4.34 The X-ray diffractograms of curcumin, chitin and BDO blends based PUs,

(KPU4-KPU6) and curcumin, chitin, BDO and clay blends based PU bio-

nanocomposites (KPU4/clay-KPU6/clay)

146

4.35 The TGA curves of polyurethane samples (KPU4/clay-KPU6/clay) and

(KPU4-KPU6)

148

4.36 The DSC curves of polyurethanes samples (KPU4/clay-KPU6/clay) and

(KPU4-KPU6)

150


polyurethane structure: (a) PU prepolymer, (b)

BDO(75%)/curcumin(25%)/clay(0.1%) based polyurethane, (c)

BDO(50%)/curcumin(50%)/clay(0.1%) based polyurethane and (d)

BDO(25%)/curcumin(75%)/clay(0.1%) based polyurethane

155

4.38 The SEM images of curcumin and BDO blends based polyurethane

elastomers, (KPU7-KPU9) and curcumin, BDO and clay blends based

polyurethane bionanocomposites (KPU7/clay-KPU9/clay)

157

4.39 The X-ray diffractograms of curcumin and BDO blends based PUs, (KPU7-

KPU9) and curcumin, BDO and clay blends based PU bionanocomposites

(KPU7/clay-KPU9/clay)

159


(KPU7-KPU9)

161


(KPU7-KPU9)

163


polyurethane structure: (a) PU prepolymer, (b)

curcumin(75%)/chitin(25%)/clay(0.1%) based polyurethane, (c)

curcumin(50%)/chitin(50%)/clay(0.1%) based polyurethane and (d)

curcumin(25%)/chitin(75%)/clay(0.1%) based polyurethane

168

4.43 The SEM images of curcumin/chitin blends based polyurethane elastomers,

(KPU10-KPU12) and curcumin/chitin/clay blends based polyurethane bio-

nanocomposites (KPU10/clay-KPU12/clay)

170

4.44 The X-ray diffractograms of curcumin, chitin blends based PUs, (KPU10-

KPU12) and curcumin, chitin and clay blends based PU bionanocomposites


172


(KPU10-KPU12)

174


(KPU10-KPU12)

176

ix

LIST OF SCHEMES

Scheme

Title Page

1.1 Preparation of polyurethane 7

3.1 Synthetic route for the synthesis of: (a) HMDI-HTPB-BDO-curcumin

based polyurethane (IPU1); (b) H12MDI-HTPB-BDO-curcumin based

polyurethane (IPU2); (c) IPDI-HTPB-BDO-curcumin based

polyurethane (IPU3); (d) TDI-HTPB-BDO-curcumin based

polyurethane (IPU4); (e) MDI-HTPB-BDO-curcumin based

polyurethane (IPU5).

44

3.2 Reaction scheme for KPU1 (polyurethane extended with 1.4-BDO (b)

Reaction scheme for KPU2 (polyurethane extended with curcumin);

(c) Reaction scheme for KPU3 (polyurethane extended with chitin);

(d) Reaction scheme for KPU4-KPU6 (polyurethanes extended with

blends curcumin/chitin/BDO).

50

3.3 Curcumin and BDO blends based polyurethane elastomers 52

3.4 Chitin/curcumin blends based polyurethane elastomers 54

3.5 (a) Reaction scheme for KPU1-clay (polyurethane extended with 1.4-

BDO/clay (b) Reaction scheme for KPU2 (polyurethane extended

with curcumin/clay); (c) Reaction scheme for KPU3 (polyurethane

extended with chitin/clay).

58

3.6 Curcumin/chitin/BDO/clay blends based polyurethane bio-

nanocomposites

60

3.7 Curcumin / BDO / clay based polyurethane bio-nanocomposites 62

3.8 Chitin/curcumin/clay based polyurethane bio-nanocomposites 64

x

ABSTRACT

In this study new series of bio-functionalized polyurethane elastomers, blends and

biocomposites with potential for biomedical applications were synthesized, employing

hydroxy terminated polybutadiene (HTPB) and different diisocyanates (HMDI, H12MDI,

IPDI, TDI, MDI) with stoichiometric balanced mole ratio of curcumin/BDO via step growth

polymerization process (1:3:2). In the same way pristine and clay based polyurethanes were

prepared, using HTPB/ diisocyanate with different blends of chitin, curcumin and 1,4- butane

diol (BDO). Characterization of the sample series was done by means of Fourier transform

infrared spectroscopy (FTIR), Solid-state proton nuclear magnetic resonance spectroscopy

(SS1HNMR), Scanning electron microscope (SEM), X-ray diffraction (XRD),

Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The FT-IR

and SS1HNMR analysis confirmed the involvement of chitin, curcumin and BDO in reaction

by appearance of broad peak of N-H at 3327.21 cm-1

and disappearance of –NCO peak at

2268.29 cm-1

in final chitin, curcumin and BDO based polyurethanes. The SEM technique

reported the surface morphology of elastomers and complete dispersion of nano-fillers in PU

bio-nanocomposites. Crystalline behavior of the synthesized elastomers and bio-

nanocomposites were investigated by X-ray diffraction (XRD), which showed crystallinity

improved by chitin and nanofiller (bentonite clay). Thermal behaviors of synthesized blends

were studied by using TGA and DSC techniques. The TGA peaks revealed that PU blends

with mole ratio 1M:0.5M:0.5M, chitin:curcumin:BDO, respectively, and 0.1% clay have

better thermal stability. The anti-bacterial and anti-fungal test for different samples of the

curcumin based polyurethanes were studied in order to determine the biocompatibility of

various diisocyanate structures based PU samples. It was found that aliphatic diisocyanate

based PU showed substantially lower antimicrobial activity as compared to the PU having

aromatic diisocyanate. Water absorption and swelling behavior of the synthesized

polyurethane elastomers and bio-nanocomposites were also observed by immersing the

samples in water and DMSO. In elastomers the chitin reduces the absorption and swelling

behavior while against of it in bio-nanocomposites clay improved both of these characters.

1

Chapter 1

INTRODUCTION

1.1 Polymer

In a polymer molecule there is huge number of monomer molecules linked with each other,

therefore, the molecular weight of polymers is much high (Gao & Yan, 2004). Material

sciences and polymer interconnects to offer a substance which has characteristics according

to current technological era. The elastomers, copolymers, macro monomers are synthesized

by using the functional polymeric materials, these are economically very useful. Near to

IUPAC meaning telechelic substances are polymeric substances possess reactive side groups

that have the ability to take part in polymer synthesis or other responses. Reactive end-groups

present in telechelic polymers known from the initial or the final or chain-transfer

components in chain polymerization, instead of monomer(s) as in polyaddition and

polycondensation (Tasdelen et al., 2011).

1.2 Polyurethane (PU)

Polyurethanes (PUs) are a broad group of materials possess carbamate connection. Hard and

soft segments in PU impart prominent features. Due to formless and crystal-like regions in

the final PU materials modify the ultimate rigidity of polymer. Shapeless areas are

characterized by random structure, in other word regular arranged areas possess of firmly

crowded even reiterating structure. Shapeless and regular arranged areas are interconnected

by H-bonding and Vander Waals forces which firmly arranged those (Nagle et al., 2007).

The PU is commonly a substance that formed by the polyaddition of diisocyanate and polyol

to get isocyanate prepolymer. After this prepolymer is converted into urea and urethane

linked materials by the reaction of diol and diamine. More remedial by urea and NCO

materials may provide biuret formulas while urethane and NCO materials create allophanates.

Near the Mary Bellis PU is an organic substance. The chemistry of PU was given in 1937

through Otto Bayer and his colloquies and developed innovative polyisocyanate-polyaddition

procedure (1902 - 1982). In 26 march 1937, the central idea about spinnable materials, that

was prepared by HDI and HDA was offered (Bayer et al., 1937).

In 1940 the manufacturing of PU elastomers were introduced on bulk level, due to

effort of ICI and Dupont. The NDI was treated as diisocyanate and H2O as chain expander.

Bayer synthesized the flexible foam during 2nd world combat, by consuming polyester gums

2

and NDI. This prepared material was applied in the arm of armed airplanes as strengthen

substances for improvement the overall competency of airplanes. In 1950 the formal way of

PU preparation was ongoing with TDI and polyether polyol by Dow chemical. By using

water, researcher of DuPont prepared spandex material by copolymerizing of TDI and PEG.

Main target of this preparation is to substitute the rubbery material. In 1959, DuPont

publicized polyether urea grit by the craft term Lycra which was synthesized by ethylene

diamine and methylene bis (4-phenylene isocyanate) (Pinten, 1943).

The PUs has been used as bio substances due to its extraordinary blood compatibility

behavior, in various fields vascular implants and tubes, non-natural heart-assisting plans. A

biosubstance is essentially a pharmacologically unique substance established for grafting in

the active structures and is frequently or occasionally pretentious to body liquid, where the

last objective is to control the employed of tissues in the physique and usual alive materials.

The altered limits are planned to compute the „„bio-compatibility‟‟ of substances (Ratner,

1993).

1.2.1 Chemistry of polyurethane

In PU, the alternating units of urethanes are connected like ester groups. By combination of

NCO and OH groups PU is prepared, this way is familiar as urethane synthesized way. PU

possessed multi atoms such as N, O and C, from this composition it is cleared, that PU is not

simply carbon based materials. The construction of a typical PU is haggard in Figure 1.1

Figure 1.1: Structure of PU

1.2.2 Raw materials for PU synthesis

A polyurethane is composed of organic units linked called carbamate groups (-NHCOO).

These groups are also called urethane linkage which is formed by an addition reaction

between polyol and diisocyanate. The reaction rapidly yields high molecular weight

materials. PU substances are prepared by the combination of two efficient components. The

one efficient component possess OH and the other contain NCO groups. The isocyanate and

alcohol groups react to create a carbamate relationship.

C

O

NH C

H

H

NH C

O

O C

H

H

O

n

3

ROH + R’NCO → ROC(O)N(H)R

’ (R and R

‟ are alkyl or aryl groups)

Table 1.1 Raw constituent’s use for PU preparation

Components Examples

Polyols Polyester PCL

Polyether PTMEG

Diisocyanate Aromatic TDI, MDI

Cycloaliphatic H12MDI, IPDI

Aliphatic HDI

Chain extender Diamines Ethylene diamine

Hydroxyl compounds BDO, HDO

1.2.2.1 Isocyanate

Isocyanates are more active substances and initially rejoin with materials possess energetic

hydrogen. Aromatic isocyanates are better than aliphatic and regarding to volume share the

largest portion among diisocyanate substances. In contrast aliphatic and cycloaliphatic NCO

provide lower volume, no doubt it is significant structure blocks for PU materials. So much

evidences are present for more reactivity of aromatic substance than aliphatic materials, and

the production is economic too. Aliphatic isocyanates are only used to get rare behavior in

end materials. By using aliphatic NCO materials, flexible and coating substances are

obtained.

The TDI and MDI are two high popular industrial level aromatic NCO substances.

TDI possess combination of 2,4- diisocyanate toluene and 2,6-diisocyanatotoluene

components. High valuable material is TDI-80 (TD-80), which consists 20% of 2,6-isomer

and 80% of the 2,4-isomer. To prepare PU stretchable slab stock and shaped foam such

combination is applied greatly. In order to get stiff foam TDI or combination of TDI with

other materials (MDI) are utilized, but has been supplanted by polymeric MDI. By changing

the combination to prepare better quality coating and flexible properties of end product

following combinations are preferred TDI-polyether and TDI-polyester. The

diphenylmethane diisocyanate (MDI) has three isomers, and is also polymerized to offer

oligomers.

4

Table 1.2 Chemical structures of diisocyanates

Name Structure

MDI CH2OCN NCO

TDI

CH3

NCO

NCO

TDI

CH3

NCOOCN

NDI

NCO

NCO

HMDI OCN CH2 NCO6

H12 MDI CH2OCN NCO

Para-phenylene diisocyanate NCOOCN

Cyclohexyl diisocyanate NCO

OCN

3,3'-dimethyl-diphenylmethane-

4,4'-diisocyanate CH2

CH3

NCOOCN

H3C

3,3'-tolidene-4,4'-diisocyanate NCOOCN

CH3H3C

5

1.2.2.2 Polyols

Polyols are hydroxy ended large molecules which possess high weight from lower value 200

to higher value 8050. These polyols play a very important role on the final behavior of PU

end products. A great list of polyols are present which is used for PU synthesis (chin et al.,

2006). But most of them falls under two classes hydroxy terminated polyesters and hydroxy

terminated polyethers.

Main kinds of polymers are such as, polyethers and polyesters. Polyols are prepared

by using propylene oxide or ethylene oxide by reaction with high working originator using

catalyst. (Alper et al., 2002). Polyesters are synthesized by period development polymer

process or reaction of pthalic acid with diethylene glycol, e.g., condensation of dicarboxlic

acids and diols (Kaszynski et al., 2003).

a) Polyether polyols

Such type of materials is categorized in different classes according to their final application,

but regarding to composition they are all obtained in same way. For example for obtaining

the polyols which give soft properties, then that types of substances are used whose

functionality is lower. But against of it if we want to prepare such type of polyol which give

hard properties than that type of substances are used whose functionality is more. Propylene

oxide is being used to get the substance whose M.W is own our requirement. Secondly also

by using propylene oxide, we get polyol with ended hydroxyl groups. As a co-reactant

ethylene oxide is applied to create varied or haphazard chunk multi materials, to modify the

coordination, rheological behaviors, and activeness of a polyol. A polyols which possess

more number of primary OH collection, are covered to ethylene oxide are high sensitive than

secondary OH assemblies.

The properties of polyols be contingent on the OH amount, OH workability, and be

contingent on the hydroxyl relationship and attraction with rest substances that take part in

chemical reactions. In order to get polyol of their own required properties then the

combinations of various polyols may be used. By applying the unsaturated polyether polyol,

we may get the subsequent properties such as antibacterial properties, outstanding clearness,

stability to hydrolysis and decent suppleness at poor heat (Tuinman et al., 2001).

6

b) Polyester polyols

These polyols are classified in two classes on the basis of its properties and chemistry. The

formal polyester materials are based on purity of raw materials i.e. by applying more-pure

glycols and diacids, polyester polyols are synthesized by the technique of direct

polyesterification. On the basis of different M.W monomers and DB, polymers can be

distinguished from each other. Its high viscosity and cost, produce certain difficulties,

however it offers good physical properties i.e. abrasion, and cut resistance which cannot be

attained by polyether polyol. The low M.W, benzene based ester polyols synthesized, by

using the other relavent materials which is needed to get the desired properties of end

products. By using the little molar quantity benzene based ester materials for manufacturing

of stiff PU foam, minimize the cost and provide outstanding antiflame behavior to PU foam.

The palm oil based polyester polyol gave better result as compared to pure polyether polyol

(Septevani et al., 2015).

On industrial level polycaprolactones and aliphatic polycarbonates are divided into

two distinct types of ester groups. By applying dicumyl peroxide as creator for the synthesis

of PCL-g-MA copolymer by combination of maleic anhydride with PCL in industry level and

in an extruder (John et al., 1997). In stiff foam methodology the polyols which is separated

from vegetal oils performs a versatile character (Guo et al., 2000).

Linear ester based polyols whose molecular weight are 2000 g are preferred for

elastomers. While for coating and foam the branched polyester polyols are used. Comparing

with polyether polyols, polyester polyols have better oxidation and thermal stability but lower

hydrolytic stability. PU adhesives were manufactured from polyester polyols and applied in

bonding rubber. Treatment of sulphuric acid on the non-polar SBR surface was observed for

the bond strength development via enhance in wettability of the rubber surface (Desai et al.,

2003). By using the polyester polyols following characteristics features can be attained:

decent resist to oils and other substances, excellent mechanical behaviors, resistance to therm

and tear asset behavior is very good, examples of those ester based polyols which are used on

industrial level are given below PTMA, PCL and PEA.

1.2.2.3 Chain extenders

In order to prepare PU materials following substances are being used due to their versatile

behavior in the synthesis of PU, resins, long particles, chain expanders (some functionality

two and some have more than two are being used), diols, polyols and diisocyanate for gaining

7

the required properties. By the phase parting of the soft and hard polymeric materials, such

that the shapeless polyether (or polyester) soft section domains cross-links between the

urethane hard segment domains, then elastomeric properties of these substances are obtained.

The formation of segments are due to mismatched of segments, that is one is polar segment

which possess better properties and against of it other possess poor properties due to non-

polar behavior. The high M.W polyols formed the soft section it has mobile properties and it

exit in the form of coiled while against of it the stiff section is prepared from isocyanate and

chain expanders which give this portion immobility and stiff properties.

For gaining the flexible properties of prepared PU, there is created a relationship

between hard section and soft section, which resist to flow of material. By giving the external

stress, the hard section became bring into line in the way of useful stress, against of it the soft

section are forced by unraveling. The strong hydrogen connection and the reorientation of the

stiff portion finally favors to tear stability, good tensile property, and stretchable. By varying

the chain expander the behavior of end substance may be varied (Blackwell et al., 1981).

The BDO, HDO and ethylene glycol are the major linear diol chain expenders. By reacting

NCO substance with the diols or diamines crystalline hard segments are formed which

increased the thermal stability and also improved the density and Tg values of final polymer (

Gerkin et al., 1994). Some important examples of chain extenders are BDO, HDO,

ethylene diamine and ethylene glycol

1.2.3 Preparation of polyurethane

Polyurethane is prepared by the reaction of diisocyanate and diol

Scheme 1.1: Preparation of polyurethane

OCN

H2

C NCO

OCN

H2

C C C

O

NH

O

H2

C NCOHN

Isocyanate (NCO)-Terminated polyurethane

m

HO (CH2)5 C

O

O H

n

(CH2)5 C

O

O

n

Polycaprolactone Diol (PCL) Methylene diphenyl diisocyanate (MDI)

O

8

1.2.4 Kinds of PU and its uses

1.2.4.1 Soft PU foam

There is a greater use of soft PU foam in daily items used articles for examples it is used as

mitigating, including wrapping, blanket, equipment, motorized centers and mat inspired due

to its bright, helpful, comfort, and durability characteristics. Almost 30 percent of this type of

foam is present in North American PU market, and mostly used in automotive and furniture

industry. The flexible, light-stable PU foam is prepared by reacting aliphatic diisocyanates

through polyether polyols and multifunctional connecting agent in the presence of H2O, a

metallic reagent and a powerful base catalytic agent (Allen & Marais, 1978).

1.2.4.2 Stiff PU foam

In order to obtain good lagging and more powerful materials, the stiff PU foam is being used

in industry. By using this type of materials the energetically maintain of required materials

costs have been reduced accordingly. In home and industry place, for getting required

standers regarding to therm and noise, consumers prefer to use such type of materials that is

polyisocyanurate foam and stiff polyurethane (Mark et al., 2002). Due to its effectiveness

regarding to insulation, it may be applied in barrier and rooftop lagging, and opening lining

etc.

1.2.4.3 Coating, Adhesive, Sealants and Elastomers (CASE)

Polyurethanes give a big and wide range of uses and compensations in the arena of sealants

and elastomers (CASE), coatings and adhesives. By using the polyurethane materials enhance

the physical properties, looking, shining and brightness of those items accordingly. To keep

powerful relation benefits PU glues are applied, but to get strengthening seal polyurethane

sealants applied. But the polyurethane materials have advantages that are molded into

different forms, stable to any environmental factor, ability to recover after stress and not

heavier than metal (Lee, 1987).

9

1.2.4.4 Thermoplastic polyurethane (TPU)

Thermoplastic polyurethane (TPU) gives better flexibility and enhances the looking of

substances, due to good mechanical, environmental and commercial properties. It may be

processed in different way by coloring, finishing or applying different technological way to

get required product. Its shaped can be modified by simply heating and cooling. Rather it

may be modified in compression, molding and extrusion technology. It provides flexible

materials that can be used for multi purposes for example used as footwear, construction and

automotive. For a huge diversity of manufacture skills it may be applied as vacuum-formed

or clarification system. Unmodified blends of two thermoplastic polyurethanes (TPU) and six

polyolefines were used to observe the effect of the component viscosities at blend

morphology and mechanical characteristics (Ptschke et al., 1997).

1.2.4.5 Waterborne polyurethane dispersions (PUDs)

The PUDs are glues and coverings substances in which H2O is applied as the elementary

substances. PUDs are being applied for big commercial and industrial scale uses due to non-

heat stability of organic solvents present in common PU, emit dangerous air pollutants

(HAPs) into the environment.

1.2.4.6 Apparel and appliances

PUs has a greater uses in textile industry, which give textile product to extraordinary

properties due to its unique behavior by its on chemistry. In garments industry the uses of

polyurethanes are being increased day by day. Spandex fibre, elastic materials and covering

substances are prepared from PU materials by several years. By improvement of

polyurethane techniques, researcher may introduce a series of new invention of apparel items

with the combination of textile industry to leather and other industries.

The major applications of hard PU foams are in refrigerator industries. The rigid PU

facilitates as an economically cheaper material which fulfill all required properties of end

users that is air conditioned and refrigerators. The well isolate-cell foam surface properties

and cell exhausting that break the hotness transmission help to achieve the better insulation

character of rigid PU foams.

10

1.2.4.7 Automotive and electronics

Polyurethanes have a versatile uses in automotive industries for making the interior and

exterior parts of auto. For getting the soft touch properties of interior parts of cars

polyurethane plays a versatile role in this area. Inspite of it PU materials attract its users

regarding its versatility, that is by using it a lengthy travelling became easy due light parts of

PU materials, and in this way the fuel expanses are also reduced accordingly.

For encapsulation, sealing and cloister delicate, sensor ability, small electronics parts,

water proof wires, and circuit series, hitting materials, anti-frothing polyurethanes substances

are frequently applied polymer. For gaining the adverse properties of PU in electronics

industry researchers are trying to give such type of PU which possesses hitting materials. By

applying polyurethane we can accept electronics device by availing outstanding dielectric and

glue characteristics, as that extraordinary flush, H2O and very high infection stability

(Goerrissen et al., 1988).

1.2.4.8 Flooring and furnishing

Polyurethane may be used by various ways in order to achieve the required position of a

researcher. Polyurethanes may also be applied to develop the grounds, we walk on daily more

strongly, therefore it is needed of such type of floor in which we can walk comfortably. If we

use such type of carpet and mat in our homes and offices which are made of PU materials can

enhance the life of floors. By using PU made mats and carpets several parameters can be

better, that is cost can be reduced and also reduced the noise problems. Polyurethanes are

mostly applied to fur grounds, from flooring and lumber to adhesive. By using such standard

materials the mechanical, washing, dry cleaning properties became better than before. By

applying the polyurethane finish the ancient ground may be refinished to look new again.

In order to decorate the home articles that are almery, doors, chairs, table‟s etc

polyurethane soft foam plays a versatile role for such type of improvements. Inspite of it

other home or office articles made more soft touch by using the PU materials for this

purposes (Brains, 1969; Hepburn, 1992).

11

1.3 Bio-functionalized PU Materials

Polyurethanes consist of hard and a soft segment, that is segmented portions are present,

which enhance the properties of PU and make it to be used in different fields of life. PUs has

possible collection of industrial uses as it may modify by its own required way to reach their

target (Zia et al., 2007). Although PU has large applications but due to non-biodegradable

behavior it was incorporated with different biomaterials such as starch, chitosan and chitin.

PUs itself possess bio concern properties, by using other biomaterial as incorporated

materials for enhancing the mechanical and bio concern properties the chitin as crosslinker

material is incorporated in PU backbone. Comparing the bio materials with each other, it was

come out that chitin in all these possess better wound healing behavior as compared to other

substances in bio sciences field. A polymer or other synthesized substances in which chitin is

used as incorporated materials, the antibacterial, and biodegradability properties of that

relavent substances became more better than before which give good behavior in commercial

scale (Miyashita et al., 1997). Curcumin (CUR) is that material which is used in biomedicine

for treatment of different diseases and complications. Due to this approach of curcumin its

demand is being increased with the passage of time. Although it has several benefits but due

to poor solubility make its uses limited. However, the biopolymers are unable to compete

with synthetic polymers (PE & PP) regarding to mechanical and thermal properties race.

Therefore it is needed to maintain these properties, such as thermal and mechanical of

biopolymeric materials by using bio-nanocomposite technique. The polymer nanocomposite

technique considered better route to update the characteristics of substances (Maiti et al.,

2002).

1.4 Chitin

Chitin and chitosan (CHI) due to good biodegradability and biocompatibility are considered

useful polymers. It has also been used as wound-healing dressing materials. In latest research

it has been shown that chitin, chitosan and their derivatives are useful for drug carriers and

also found low toxic materials. Chitin can be extracted from three sources, namely

crustaceans, insects and microorganisms (Muzzarelli & Muzzarelli, 2005). Inspite of these

benefits, chitosan has been found to damage the cells including red blood cells. But the 6-O-

carboxymethylchitin and N-succinyl-chitosan are low toxic materials (Kishimoto & Tamaki,

1987).

12

Chitin is that material which is found abundantly in nature from the shells of shrimp, crab and

squid pens. Chitin and its derivatives have been applied for a various applications such as

textile, food, water treatment, agriculture, wound dressings and in bio technique because of

its availability, biodegradability as well as biocompatibility (Goosen, 1997). Chitin, regarding

to its occurrence is generally found in upper layer of sea living organisms, secondly it is

easily achievable and is found abundantly in nature. Because it has no harmful effect on the

environment therefore much of researchers refer the use of chitin. But poor solubility in

organic solvent and water resists the use of chitin in vast fields of applications. For obtaining

the solubility of chitin in water, the chemical modifications of chitin material is required. The

oxidation of chitin material at C-3, C-6 may be able it to solubilize in water by introducing –

COOH groups onto –OH (Sun et al., 2006).

OH

H

NHCOCH3H

OH

CH2OH

H

OH

H

NHCOCH3H

OH

CH2OH

HO O

n

Figure 1.2: Structure of chitin

1.5 Curcumin

Curcumin is polyphenolic materials are extracted from turmeric, its structural formula is

presented in (Figure 1.3) and other by product who‟s all general sources is turmeric. The

major component in the flavor of turmeric is curcumin. The Indian literature reported that it

has low M.W and good medicinal properties. Due to its antiproliferative, antiangiogenic,

antioxidant and anti-inflammatory properties, the interest of researcher in it has been

increasing day by day (Aggarwal et al., 2003). The effects of CUR also studied in vitro and in

vivo replicas (Aggarwal et al., 2013; Chin et al., 2013; Reddy et al., 2013).

OH

OCH3

HO

H3CO

O O

Figure 1.3: structure of curcumin

13

Curcumin has ability to face savior problems, such as inflammation, bacterial infections and

also ability to recover the damaged organs of body in better way (Kulac et al., 2013). As a

free radical it shows its behavior as antioxidant, and it is recommended for recovering the

inflammation problems during wound treatment (Mohanty et al., 2012). Such behavior of

CUR regarding wound treatment is due to its biochemical behavior as works against

inflammation, infections etc (Ak and Gulcin, 2008) actions. It works by involvement with

tissue or support to regenerate the demage part of body in fruitful way by collagen collection

to promote the dead part to active way (Joe et al., 2004). Different reporter reported that its

uses promote the regeneration process actively also increase the vascular mass (Sidhu et al.,

1998).

1.6 Clay

The previous reported work report that by incorporation clay as reinforcement in polymeric

matrix enhances the properties of polymer according to target. The clay is formed by

composing the mineral particles, its composition formula is given as [(Na, Ca) (Al, Mg, Fe)

(Na, Ca) (Al, Mg, Fe)6 (Si4 O10)3 (OH)6]. Its formula shows that in which alumina and silica

give special relation (Grim, 1968). The over way concentration of negative charges on whole

covered to positive particles present in structural formula. Poor electrostatic forces create the

parallel layer behavior in formula (Parker, 1988). The presence of positive particles in

structure plays a fruitful role to create intercalation materials for getting the end product

materials (Patterson & Murray, 1983).

Although several nano substances are available but clay in which the special relation between

alumina and silica exit, and possess parallels of alumina silica which create the potency

between organic or inorganic substances for the preparation of nano-composite materials

accordingly (Ray & Okamoto, 2003). The clay material is being used for giving the good

thermo-mechanical behaviors of synthesis nano-comosites and also enhance the applications

of treated materials in better way (Dong & Feng, 2005; Tunc¸ & Duman, 2011). Inspite of it

the clay using trend is being increased day by day for recovering the loosing properties of

bio-based polymer by incorporation of there in main backbone of polymer, which possessed

biocompatibility and biodegradability properties (Yadollahi & Namazi, 2013; Buchtová,

Lack, & Bideau,2014).

By the combination of polymer substance and nanomaterials, the nano-composite is

prepared in which polymer act as matrix and clay act as reinforce, which possess one side in

14

nanometer approach. By adding the nano-filler in polymer materials, most of its properties

have been improved.

1.7 Aims and Objectives

Keeping in view the outstanding anti-oxidant, anti-cancer behaviors of CUR,

biocompatibility and wound recovering behaviors of chitin, decent heat stable characteristics,

elastic behavior and compatible with living organisms characters of PU and good surface area

properties and better gaining the thermo-mechanical characteristics of polymer by bentonite

clay there is an extreme need to bring a polyurethane, which possess biodegradability,

biocompatibility and biofunctionality. None of the researcher has given the thermo-

mechanical and surface properties of curcumin/chitin/BDO blends based PU elastomers and

curcumin/chitin/BDO/clay based PU bionanocomposites. The study has been conducted with

following aims and objectives:

To synthesize novel curcumin based PU elastomers varying diisocyanate structure.

To synthesize novel curcumin/chitin/BDO blend based PUEs.

To synthesize novel curcumin/chitin/BDO blend based bionanocomposites.

To study the structural, biological, surface and thermal characteristics of

curcumin/chitin/BDO blend based PUEs and bionanocomposites.

To explore the effect of curcumin, chitin, BDO used as chain extender in the

synthesized polymer and bionanocomposite samples, and “data interpretation and

mechanism explain were also discussed” was also the objectives of the thesis.

15

Chapter 2

REVIEW OF LITERATURE

2.1 Polyurethane and Polyurethane Based Materials

Polyurethane is that material made of organic units combined by carbamate (urethane)

relations has wide variety of uses as their properties may be modified by variation of their

monomers (Yamazaki et al., 1997). Varying the structure of segmented polyurethane (hard

and soft segments), the characteristics of materials altered according to targeted way.

Polyurethane elastomers (PUEs), due to their biocompatible properties are considered as

unique polymer (Zia et al., 2009). In medical field heart valves, blood-contact things

(Hoffman et al., 1993), and transplants for the knee combined meniscus, insulators for

pacemaker, electrical clues, cardiovascular tubes (Klompmaker et al., 1993).

The biodegradable PUs is synthesized by using ester polyols and simple chain

expenders. DCE founded by degradable materials to promote the stiff portion, degradation

was also developed (Tatai et al., 2007).

The preparation of PUs, and its characterization (spectral, surface and thermal) was

presented by using diisocyanates and diols (Zia et al., 2009; Rogulska et al., 2006; Zia et al.,

2009). The PUs was functionalized by incorporating various materials that is sugar (Garc et

al., 2001), a biomaterial in which chalcone is incorporated in PU backbone (Sivakumar et

al., 2012; Daemi & Barikani, 2012) chitin incorporated polyurethane for thermal response

(Chen et al., 2012) have been documented and reviewed. Surface characteristics of cellulose

(Yokota et al., 2008) starch (Matsushita et al., 2008), and triolein injected polyurethane

(Santosa et al., 2008) studied and organized. The PU functionalized by PMMA and vegetable

oil (Zhang et al., 2012), the PUDs incorporated with nano cellulosic material and

bioantifelting agent (Zou et al., 2011), PU functionalized by canola oil and PMMA (Lee &

Kim, 2012). The interaction of nano-starch material and cellulosic particles with PUDs was

studied (Wang et al., 2010). The preparation and characterization (structural, thermal and

crystalline pattern) of chitin supported PU was presented (Zia et al., 2008; Zia et al., 2009;

Zia et al., 2010) Researcher also reported the synthesis and applications of HTPB-based

polymers (Daemi et al., 2013).

16

Fiala et al. (1987) introduced segmented polyurethanes which are differing in composition

and structure and inducted in the left portion of hearts of different goats upto 72 h. Then

specimens were observed visually regarding to formation of thrombi, by removing in place of

treated. Then characterized in order to examine the synergetic behavior of PU with blood

using XPS, SEM and infrared (IR) reflex ion spectroscopy. In the end it was concluded that

the compatibility of PUs with blood can be improved by applying different way.

Takahara et al. (1991) investigated the properties of segmented polyurethanes such as

bulk, surface and blood contacting by using different polyols. Polyethylene oxide,

polytetramethylene oxide, polydimethyl siloxane and hydrogenated polybutadiene were used

during this synthesis. Hard segment was composed of BDO and MDI. The segmented

polyurethanes have the water resistance polyols such as hydrogenated poly(butadiene) and

poly (dimethylsiloxane) gave prominent separation in hard and soft parts. The lowest platelet

adhesion was observed for polydimethyl siloxane PU as compared to other segmented

polyurethane.

Zia et al. (2007) presented the reported work of PU and PU composite material

regarding its recovery and recycling process. The different kinds of waste PU materials,

which include recycling substance or production residue, are commonly abridged to a much

beneficial size, e.g granules, etc. It all depends on specific kind of PU that comes to

recycling. The different reprocessing methodologies for substance and chemical changing of

PU, have mostly helpful for improving the reprocessibility of PU in latest years, but the most

common technique for recycling of PU is glycolysis. Therefore in this way new

methodologies were introduce for reprocessing PU and PU composite. PU foam that is used

in auto industry has been bitterly reprocessed by regrinding methodologies. Although the

glycolysis of PU is a cheaper way, but further improvement is now required in order to

control more damaging in the rest-consumer material. It is concluded that the recycling

processes for plastic feedstock technically acceptable and vigorous sufficient to grant more

progress in coming days.

Jiang et al. (2007) synthesized the waterborne polyurethanes that has

biodegradability, biocompatibility and has good mechanical properties, using PCL,

isophorone diisocyanate (IPDI), PEG, BDO and l-lysine instead of using other substance. The

synthesized polymers were then characterized by using different analytical techniques that is

IR and DSC, based on the quantity of PEG. The Lipase enzyme was used to analyze the

17

biodegradability. The resultant synthetic waterborne PU had very better tensile strength,

which can be used as biomaterials. Change in the amount of PEG changes the tensile

properties and microphase division, interpreted by IR and DSC data.

2.2 Curcumin and Curcumin Based Materials

Curcumin, although has hydrophobic behavior but it is being used in textile and in food

manufacturing era as colouring materials. The CUR possesses antioxidant, anticancer, and

anti-inflammatory behavior, therefore its demand is increasing with the passage of time

(Aggarwal & Harikumar, 2009). In contrast to its several beneficial properties CUR has low

oral bioavailability in both human beings and animals (Anand et al., 2007) due to low

resistivity and solubility. The solubility grade in water having acidic media in only 11 ng/ml

(Tonnesen et al., 2002) and in neutral media the process of solubility much decreased. In

alkaline medium or in buffer solution, CUR degraded hastily (Priyadarsini, 2009; Wang et

al., 1997). The chemistry of CUR plays a versatile role in bioactivity character of CUR (Ruby

et al., 1995).

For treating the human being diseases in India, CUR is used for recovering from

harmful problems such as disorders, cough, diabetic ulcers etc. According to researcher the

combination of CUR cream with lime may be used for treating wounds and inflammation as a

home remedy (Anamika, 2012).

Mahmood et al. (2015) overviewed that for treating the human being diseases in

India, CUR is used as remedy. The diferuloylmethane give color to CUR, which is present in

turmeric substance. Curcumin due to its free radical properties it is being used for the

treatment of several complications such as inflammatory, carcinogenic etc. In present study

presented the data of different researcher regarding to biomedical uses of CUR based

substances. The main point of this study is that in which the problems of human beings

regarding to different diseases which turn into a harmful way by creating the carcinogen

effect, diabetic effect, in vitro and vivo problems effect etc are discussed and their treatment

with different evidences are discussed and resolved. Although a CUR has several beneficial

properties but sides of it, it has few drawbacks which reduce its bioavailability in different

areas accordingly. For overcomes these problems different proposal and highlighted the

different hot areas that are beneficial for human in future are discussed and proposed their

remedies accordingly, also discuss in present review with reference to different reporter.

18

Mahmood et al. (2016) synthesized PUs materials, using CUR/BDO and by changing the

morphology of diisocyanates. The FTIR technique confirmed the structure of final PU

material. The SEM technique is used to know the complete homogeneity of participated

materials accordingly, and also know the surface structure. From this SEM results it has been

cleared that prepared materials are hereby confirmed that, the diisocyanate plays a vital role

for its structure. The aromatic diisocyante plays a crucial role in phase separation as

compared to aliphatic based PU, which also revealed by SEM. The bio-compatibility of

synthesized PU materials was confirmed by performing anti-microbial tests. From these tests,

it has been cleared that aromatic based PU possessed more biocompatible behavior as

compared to aliphatic based PU. Actually, this is a little struggle for introducing novel

biocompatible materials.

Mahmood et al. (2016) reviewed the poor accessibility of CUR regarding to its

drawbacks, such as fast degradation and poor absorption and slow medication. In this study

regarding to face mention problems of CUR are discussed with respect to different

approaches such as liposomes, nanocomplex and possible for the transfer of CUR to its

required place accordingly. If CUR is combinated to chitosan (CHI) and its modify form than

the working activity of CUR is increased. In this review discuss the way by using different

substances that enhance the therapic activity of CUR by blending with these materials such as

cyclodextrin, starch, dextran sulfate etc and in this way new approaches will come before

researcher regarding to human beneficial that is clinical uses. If used different drug delivery

system for target approaches of CUR to their required sites, such as CHI blend

polysaccharide, amino acid based drug delivery and metal based etc increased the efficiency

of CUR positively. In this review try to arrange the different approaches, methodologies and

way to enhance the CUR biological activities by using different researcher work as a

references.

2.2.1 Biomedical uses of curcumin and its blended substances

Curcumin due to its free radical properties it is being used for the treatment of several

complications such as inflammatory, carcinogenic etc. In present study presented the data of

different researcher regarding to biomedical uses of CUR based substances. The main point

of this study is that in which the problems of human beings regarding to different diseases

which turn into a harmful way by creating the carcinogen effect, diabetic effect, in vitro and

19

vivo problems effect etc are discussed and their treatment with different evidences are

discussed and resolved.

2.2.1.1 Nano-technique curcumin has therapist properties

The working ability of CUR can be enhanced by grinding the substances upto nano form for

gaining optimic properties. This technique presented a very fruitful effect on the overall

CUR activities accordingly, actually in this way the surface areas of materials are increased

which ultimately improve its all activities as compared to other technique, it showed effects

on glioma cells (Tagami et al., 2014).

2.2.1.2 Curcumin and resveratrol encapsulation

If we blended two such types of substances that are both obtained from natural sources, then

the resultant product possess extra ordinary properties accordingly for example if we

combined resveratrol and CUR then the resultant products give better output. Keeping in

view the bio properties of both these materials showed good antioxidant characters, due to

formation of free radical behaviors, especially to tackle the DNA problems and internal body

problems (Leonard et al., 2003). If we observe the literature work regarding to these

materials it became cleared that the blending of these both substances give positive effect by

combine working (Malhotra et al., 2010). But the major problems of both these materials are

their poor solubility, weak bio behaviors and lacking of stability against light that is UV light,

but such complications are covered by using the nano techniques because this technique

overcome previous mention problems accordingly (Coradini et al., 2014). Step by step

techniques of capsulation of CUR also studied in detail (Kittitheeranun et al., 2015). Step by

step techniques of capsulation of CUR were processed by electric technique that is self-

combination technique (Figure 2.1). By following this technique positive particles are

attracted to negative particles to form uniform layer at calcium carbonate surface. After the

formation of layer it is separated from calcium carbonate surface by dissolving it in EDTA

solution, in the core water insoluble drug carry materials are now ready for further

proceeding. In Figure 2.1 the whole process is discussed in detail step wise that in first step

the calcium carbonate layer or template is coated with positive particles, after this the positive

layer is further layered with opposite charges that is negative layer particles, this step by step

coating remain continue by opposite charge particles until at the end targeted stage is

reached, when process of step by step coating is completed than the template is removed by

20

dissolving in EDTA solution now the required capsule is ready, now this capsule is ready for

filling with drug substances that is CUR, this drug is now released in buffer media.

Figure 2.1: Schematic representation for the formation of hollow nanocapsules via

electrostatic layer-by-layer (LbL) self-assembly, drug loading and release

(Kittitheeranun et al., 2015).

2.2.1.3 Curcumin stimulated wound covering

When in system of body disordeness is created and complication process enhanced the

diabetic produce that change the structure of body organ that is wound healing process is also

disturbed. Relationship between diabetes and complex situation disturb healing process.

Curcumin due to its free radical properties it is being used for the treatment of several

complication such as inflammatory, carcinogenic etc. In present study presented the data of

different researcher regarding to diabetic uses of CUR based substances. Due to diabetic

disease the whole organs of body disturbed by this the other defensive activities of whole

physics also changed which causes to delay in coverage of wound (Dissemond et al., 2002).

Due these variation the oxidation process became more fast accordingly, and the resultantly

the wound healing process became more passive. By these complication of extensive increase

in oxidation therefore it became a dire need to use such materials which stop these oxidation

process and inflammatory rate accordingly. (Dissemond et al., 2002). According to literature

report it is cleared that CUR possesses good antioxidant and anti-inflammatory characters,

which able it to a rare material for dressing wound covering problems in diabetes patients

(Kloesch et al., 2013). In this work a group of rats that possess diabetic symptoms and a

group which did not such problems are study comparatively by using the CUR substances as

21

medicine for overcome these problems accordingly. The positive result suggest that CUR-

CUR act as good anti-inflammatory and antioxidant (Kant et al., 2014).

2.2.1.4 Curcumin derivative applied against diabetic problems

The diabetic patients are faced a several problems regarding to internal body structures that is

retinopathy, nephropathy, neuropathy and cardiovascular disorders, CUR derivatives covered

these problems very positively to maintain the internal phenomenon by reducing oxidation

process (Callaghan et al. 2005). But in many cases when the level of glucose is enhanced

from more much high stage, where insulin is injected in that era of patient to cover the

dangerous situation accordingly, due these variation the oxidation process became more fast

accordingly, and the resultantly the wound healing process became more passive where the

derivative of curcumin play versatile role for covering such situation (Rolo & Palmeira,

2006). In reported literature it is cleared that by inducing different derivatives in effective

patients the result showed that by inducing the materials presented the result in such way,

under hyperglycemia, the increased ROS generation in mitochondria, increases the flux of

glucose into aldose reductase (AR) pathway, and increases the flux of sugar into hexosamine

(HA) pathway (Shen & Ji, 2012). From the results cleared that the effect of antioxidant and

anti-inflammatory actions power have excessive beneficial potentials, as the oxidative

problems and inflammation now show to be basic device original a much of human

disturbance, as such diabetes (Chuengsamarn et al., 2012). Thus the CUR which definitely

controls the antioxidant defense system and shows inspiring anti-inflammatory behaviors

(Chuengsamarn et al., 2012). The present of functional groups such as methoxy, phenoxy,

and carbon–carbon double bonds in its structure stimulate the antioxidant behavior in

polyphenolic CUR substances. More research by using the rational drug project on these

morphology may lead to explain of novel class of controlling anti-diabetic drugs in future

(Yousefia et al., 2015).

2.2.1.5 Curcumin behave as antibacterial material

In textile field the researcher are interested in antibacterial textile finishing for last many

years. Although there are several antibacterial agents are being used in textile fields before

but they are all have some sides effect in minor or major form, but against of all these CUR is

a best antibacterial agent that do not have any toxic behavior. Curcumin also act as good

natural dyeing agent without any major toxic situation. It has also been originate to show a

broad choice of pharmacological happenings (Shen & Ji, 2012).

22

2.2.1.6 Neuroprotective achievement

In reported previous work there is shown that curcumin act as good neuroprotective materials

but due to regeneration problems it is not considered good material. Curcumin due to its free

radical properties it is being used for the treatment of several complication such as

inflammatory, carcinogenic and neurotoxicity etc. Curcumin definitely controls AMP kinase

(AMPK) performance and this exploit favors to the organization of metabolic disorders

(Soetikno et al., 2013).

2.2.1.7 Anti-cancer action of curcumin based nano-materials

In men most common form of cancer is prostate cancer. In U.S year 2014 there is a

calculation data is presented regarding new put cases and death cases such as estimated

233,000 new cases and 29,480 deaths respectively. Although this cancer disease is curable

but so much costly cannot be afforded (Snyder et al., 2010). The CUR which definitely

controls the antioxidant defense system and shows inspiring anti-inflammatory behaviors.

Epidemiological results show that natural polyphenol substance used in regular diet reduce

the hazard and frequency of different kinds of cancers (Sinha et al., 2003). Among numerous

natural anti-cancer mediators, curcumin is a promising phytochemical that has established

remarkable therapeutic possible for prostate cancer (Aggarwal, 2008). Sequencely, new drugs

are desirable to treat progressive hormone-resistant prostate cancer (Feldman & Feldman,

2001). The potential of CUR to tackle both androgen-dependent and androgen-independent

cancer created material has been explained by the in vitro and in vivo research. The CUR

helps as a good instance of a class of complexes that is bright to mark multiple enzymes with

a “magic shot gun” (Brown et al., 2013).

2.2.1.8 Efficacy of Curcumin in the covering of paracentesis in rats

Curcumin (diferuloylmethane) is principal energetic substance in the flavor turmeric

(curcuma longa). It is basically a low molecular weight natural polyphenol with excelent

medicinal assets which are well reported in ancient Indian literatures. Curcumin is a

polyphenol and possesses anti-inflammatory, antioxidant, antiproliferative, and wound

healing properties (Anand et al., 2007). The disease portfolio for this traditional medicine

includes pain disorders, digestive diseases, menstrual difficulties, skin conditions, sprains,

wounds, and liver disorders. In vivo, wound healing is significantly more multifaceted than in

vitro, linking three (partially overlapping) phases: inflammation, tissue creation and

23

remodeling (Singer & Clark, 1999). Curcumin recovers wound covering phenomenon in

paracentesis of TM. By applying CUR doses, the closured paracentesis part was seen close to

the usual eardrum; and chunkiness of the TM and sclero-sis were decreased than the standard,

viewing the enhanced curing at15th day (Birdane et al., 2014). Curcumin summarized pH

sensitive jelly based IPN materials system nanogels for anticancer drug distribution has been

reported in the literature (Jelezova et al., 2015; Rao et al., 2015). The NGs were over network

with GA to design resist IPN-NGs. The amphiphilic SDS molecules could prolong nucleation

and hinder the growth of gel particles (Rao et al., 2015). The results exposed that CUR

loaded substances used for the cancer therapy highly enhanced recovery and cured (Some et

al., 2014).

2.2.1.9 Curcumin applied in the finding of HCIO

In our daily life there is greater use of hypochlorite (ClO−)

and its protonated form (HClO).

Sodium hypochlorite is regularly applied as the active materials of 84 antiseptic and

bleaching item. In living beings, hypochlorite is prepared from H2O2 and chloride ions in a

chemical response catalyzed by the enzyme myeloperoxidase (MPO) (Sun et al., 2014).

Hypochlorite, since of its powerful nucleophilic non-radical oxidability, is a key antibacterial

substance that is applied for regular protection. Though hypochlorite purposes mostly in the

saving of microsubstances invasion, enhancing evidence purposes that abnormal stages of

hypochlorite may approach to tissue spoil and diseases such as atherosclerosis, arthritis, and

cancers (Huo et al., 2012). But, the apparatus of act of hypochlorite in these problems is still

not entirely under-stood since of the absence of subtle and precise probes for noticing. Up till

now, the hypochlorite glowing inquiries, which have been prepared and used to hypochlorite

finding, are much p-methoxy phenol byproducts (Cui et al., 2010; Sun et al., 2008), oxime

byproducts (Zhao et al., 2011) and rhod amine byproducts (Xu et al., 2013; Koide et al.,

2011) with the predicament of complicated multi-step synthesis, poor production and in

surmountable bio-toxicity. Here in, we presented the regular drug-CUR as an outstanding

choosiness, compassion inquiry for the analysis of hypochlorite dual in biosystem and

industry analysis (Yuea et al., 2014). The supposed way for the checking of hypochlorous

acid is presented in Figure 2.2. The natural drug CUR (1) showed much choosiness and

sympathy for hypochlorite in MeOH/HEPES. Because of its extraordinary functioning and

commerce property, the sensor has potential uses in physiological and environmental

structures for hypochlorite finding (Yuea et al., 2014).

24

Figure 2.2: Proposed mechanism of the recognition of hypochlorous acid using

curcumin (Yuea et al., 2014).

2.3 Chitosan/Chitin Based Materials

Chitin (C8H13O5N)n is that polymer which is present abundantly in nature, it is present

naturally in the external wall of living organism, such as microorganism, external hard shell

organisms and mushrooms. Its structure is very compact and hard due 1,4-2-acetamido-2-

deoxy-β-D-glucose monomers (Muzzarelli, 1997). Chemistry of this polymer resembles with

cellulose, but in it carbon number two acetamide group is attached rather than –OH group

therefore it is called amino polysaccharide. Due to flocculent properties of chitin and its

derivatives, it is being used for treatment of waste water. However due to multiproperties of

chitin and its derivatives trend is being changed for producing worth yields for cosmetic,

medicinal, pharmacological and biotechnological use (Kurita et al., 1986). Due to non-toxic,

antimicrobial, good biocompatibility and biodegradable properties of chitin and its

derivatives have versatile attractiveness for use in large commercial level (Miyashita et al.,

1997). In order to better the solubility and processibility of chitin, the researchers have been

trying for last two decades (Chandra & Rustgi, 1998; Jang et al., 2004; Kurita, 2001; Kurita

et al., 1986; Muzzarelli, 1997; Rinaudo, 2006).

Regarding to its occurrence chitin is the second most significant natural polymeric

material in the world. Marine animals , shrimp and crabs are the major sources of chitin

availability. Rinaudo, (2006) reported the situation of the art regarding this polysaccharide,

its structure in the innate dense state, procedure of analysis and classification and chemical

25

changes, as well as the problems in using and dispensation it for nominated uses. The

production of chitin almost same to cellulosic materials, regarding to its chemistry it is a

amino polysaccharides. The uses of chitin has been increased due to novel behavior of this

substance with other other to prepare a material of its own desire properties, and recent

development in chitin chemistry is fairly notable (Kumar, 2000).

Chitosan (deacetylated product of chitin) is that substance which is attained from

chitin regarding to its properties it is a non-toxic and bio-degradable material which possess

broad uses. In biomedical field both chitin and chitosan (CHI) have equal importancy,

because it can be modified according to desire properties, uses and adjustment era. Although

it is present in large amount but due to drawback of chitin in field of solubility and

interactibility, its uses has been decreased (Pillai et al., 2009).

Zia et al. (2010) prepared shape memory polyurethanes by using MDI and

polycaprolactone diol 4000 (PCL 4000) as monomers and chitin, BDO, triethylamine (TEA )

and DMPA as chain extender. After synthesis the polymer samples were irradiated with UV

lights by changing the time duration i.e. 50, 100, and 200 h. By measuring contact angle,

water absorption and balance degree of swelling was investigated the properties of time

duration in UV-irradiated PU samples. From the final results it has been cleared that by

increasing the time duration the properties of the samples were affected. The reaction of PU

layers with solvent on the superficial were correlated to the amounts of chitin and DMPA in

the end PU synthesis and UV-irradiated time.

Jayakumar et al. (2011) explained the applications of CHI and chitin i.e. wound

dressing in much promising medical field. Due the adhesive properties of chitin and CHI

along with bactericidal and antifungal property, and their spontaneously passing to oxygen,

are very useful regarding to the remedy of wounds and burns. Much of the derivatives of CHI

and chitin had been synthesized for different uses in the form of sponges, fibers, hydrogels,

membranes, and scaffolds. The objective of this research is to know the result after treatment

of wound recovering uses of biosubstance based on CHI, chitin and their derived forms in

detail.

Chen et al. (2012) offered a chitin blend PU (TRCPU) organogel synthesized of

polyethylene glycol (PEG), isophorone diisocyanate (IPDI) and chitin. PEG was used for the

preparation of soft segments for giving hydrophilic and elastomeric properties to polymer.

Chitin and IPDI were used for the synthesis of hard segments because it contains well polar

26

urethane linkage. The level of acetylation and the mean molecular weight of chitin were

evaluated based on the internal viscosity. In PU chitin was added through covalent bonding,

after chitin addition the polymer obtained had an injectable organosol at minimum

temperature while at higher temperature it was converted into semisolid organogel. The

synthesized polymer was characterized by using different techniques, 1H NMR, FT-IR and

DSC.

2.4 Chitosan/Curcumin Based Materials

For gaining the biomedical potency of CUR based substances, there are many approaches are

used to get desire materials, for example preparation of various chemical derivatives to

enhance its water solubility as well as cell up take of CUR. Thus, the conjugation between

CUR and CHI potentiate the sustainability, anti-proliferative and apoptotic activity of CUR-

CHI blend material. Following are the potential properties of CUR /CHI based materials are

discussed.

2.4.1 Chemical interaction between curcumin and chitosan

For studying the interaction between CUR and CHI the molecular mimicry is used. If we

examine the reaction structure of CUR and CHI by using the geometric technique, there is

seen hydrogen bonding interactions as shown in Figure 2.3 (Pourreza & Golmohammadi,

2015). Due to presence of glucosamine unit in chitosan, so there is great affinity between

CUR and CHI at high pH level from 7 to 10.5. Due to presence of two hydroxyl groups (-

OH) in the benzene ring and the hydroxyl near keto group (C=O) in CUR has intramolecular

hydrogen bond is the basic interaction. Many reporter reported that there is hydrogen bond

between -OH and C=O (Sharma et al., 2005). In pH limit 3-7 CUR shows characteristic keto-

enol tautomerism and the enolate practice chiefly. In Figure 2.3 this behavior can be seen

clearly. But from the reporting result it is cleared that promonent interaction between CUR

and CHI is present, if surfactants is used with them at physiological pH. The binding process

between CUR and CHI is known by thermodynamic studies (indicated by both enthalpy and

entropy) hydrophobic, electrostatic and hydrogen bond formation (Boruah et al., 2012).

The amino groups (protonated NH3+

) of chitosan and negatively charged moieties i.e.,

carboxylate or sulfonate groups, of protein carbohydrate chains yields CHI-coated

nanoparticles interrelate with mucin due to electrostatic interface (Svensson et al., 2008),

27

subsequently, this communication may be valuable to delay the contact time and presentation

of drug (CUR or others) carrying systems at mark site.

Figure 2.3: Hydrogen bonding interactions between curcumin and chitosan molecules

(Pourreza & Golmohammadi, 2015).

2.4.2 Preparation of CUR-CHI nanoplex

For the formation of soluble CUR–CHI complex, first of all curcumin as dissolve in basic

solution to create a charge molecules, then after this this dissolved curcumin mixed with

aqueous acetic acid solution of oppositely charged CHI, after adding both materials a

homogenized soluble complex was formed the whole process is presented in Figure 2.4.

Masses of the soluble complex were afterward prepared due to non aquous connections

between the bound CUR materials. The value was dictated by the hydrophobicity of CUR

and CHI nanoplex was due to complex collections later segrigated out to prepare the CUR–

CHI nanoplex upon attainment a serious collective absorption, whose the strong electrostatic

interfaces between CUR and CHI particles repressed the later from collecting into arranged

ordered morphology among precipitation, resultant in the preparation of disorder CUR–CHI

nanoplex (Cheow et al., 2015). CUR having pKa of 8.4, 9.9, and 10.5 was fully deprotonated

at pH 13 to form the negatively charged CUR(3-)

with a charge density of 8.14 × 10-6

mol-

charge/mg, whereas the NH2 group of CHI (pKa 6.5) was protonated upon its dissolution in

acetic acid with a charge density of 5.58 × 10-6

mol-charge/mg (Leung et al., 2008). The

CUR–CHI nanoplex separated in water salt resolutions as a outcome of the charge

transmission outcome of the salt, leading to the release of CUR from the nanoplex . After

eight hours the strength of CUR was at nearly 76% of the fully solubility nearly 24%

deprivation of CUR in a retro of 6.5 hours. This explained that the CUR discharge from the

28

nanoplex did not feel prominent distortion in phosphate-buffered saline (PBS) in against to

formerly described work (Sun et al., 2010).

Figure 2.4: Preparation of amorphous curcumin–chitosan nanoparticle complex (or

nanoplex in short) via the drug–polysaccharide complexation method that involved the

mixing of curcumin (CUR) solution in base with chitosan (CHI) solution in acid (Cheow

et al., 2015).

2.4.3 CUR carrying CHI schemes and their potential behavior

In vitro and in vivo assessment of curcumin showed chemopreventive and chemotherapeutic

properties on different cancer cell kinds and animal replicas (Nautiyal et al., 2011). By giving

dosing much of quantity is not reached to their targeted places, therefore it is extremely

needed to make better the process of oral bioavailability of curcumin. The process of oral

bioavailability is also more needed to improve because the amount of bioavailability straight

effects on the plasma attentions, because the therapeutic and toxic belongings subsequent

after oral drug management. Moreover, chitosan blend nanoformulations presented several

benefits, such as saving and issue of the drug over a protracted retro in a standard way

(Jayakumar et al., 2010).

29

The bioavailability of CUR-loaded chitosan blend nanomaterials increase the bioavailability

and stay the holding time of CUR because of collection of nanomaterials in endoplasmic

reticulum structure. If this prepared materials is tested in vivo, than there is a very supportive

results are come out that is the process of deposition became better by using such technique

and re-epithelialization of skin CUR-loaded chitosan blended complex showed dangerous for

the parasite. It also has a potential materials for treating cancer type diseases. The NPs of this

mucoadhesive materials (chitosan) interrelate with the negatively exciting mucosal

superficial and can be helpful to extend the connection time of drug transfer system in the

mucosa, which would enhance the therapeutic working of CUR or/and other drugs

(Mazzarino et al., 2012).

2.4.4 Polysaccharide/curcumin-chitosan nano-technique

The properties of curcumin has been improved by the complexation of CUR with

cyclodextrins (CD) is a such type of approach to cover the specific properties of CUR. The

solubility of curcumin has been increased than pristine curcumin by complexation with CD,

particularly for oral transfer (Yadav et al., 2009). Masses of the soluble complex were

afterward prepared due to non aquous connections between the bound CUR materials. The

value was dictated by the hydrophobicity of CUR and CD nanoplex was due to complex

collections later segregated out to prepare the CUR–CD nanoplex upon attainment a serious

collective absorption, whose the strong electrostatic interfaces between CUR and CD

particles repressed the later from collecting into arranged ordered morphology among

precipitation, resultant in the preparation of disorder CUR–CD nanoplex. Higher solubility of

CUR-CD complex in aqueous solution focused to more interface between CHI (positively

charged) and CUR-CD (negatively charged) complex bring about in more filling addition in

nanoparticles. It is described that CUR-CD-CS nanoparticles presented to be greater in vitro

drug issue presentation and high harmfulness against human skin cancer cell line (SCC25),

leading to nearly 100% apoptotic cell death (Bansal et al., 2011).

A sheet like film is made up of β-Chitin containing CUR were designed through a

water-blended scheme to straight a ailment of being harmless. For carrying Tween

20/curcumin, a chitin sheet was used which is made up of small fibre particles. The human

skin may be treated with β-chitin non-woven fibrous films comprising curcumin might be a

talented contender as a drug delivery device (Ratanajiajaroen et al., 2012). The entrapped

30

curcumin in the Tween 20 micelles remain stable up to three days. The whole above mention

properties and their whole mechanism is illustrated in below Figure 2.5 in detail.

Figure 2.5: Proposed scheme illustrates the presence of the solubilized and unsolubilized

curcumin in the chitin sheet in a phosphate buffer solution (pH 7.4) at 37 °C

(Ratanajiajaroen et al., 2012).

Crosslinked CHI materials synthesized via different crosslinkers, such as

glutaraldehyde, suberoyl chloride, asgenipin, and epichlorohydrin imparted controllable

water absorption and drug release properties and use for biomedical applications. In pH limit

3-7 CUR shows characteristic keto-enol tautomerism and the enolate practice chiefly. But

from the reporting result it is cleared that promonent interaction between CUR and CHI is

present, if surfactants is used with them at physiological pH. It was observed that against

CHI, cellulose crystals presented as a diffusion barrier unlike the discharge of CUR

molecules from the sheet samples (Bajpai et al., 2015).

It is stated that by adding of starch particles increased the motorized strength of CHI-

TPP blobs. Bajer and coworkers deliberated the inter-molecular connections between the CHI

and starch in their mixture (Bajer & Kaczmarek, 2010). The chitosan-starch blends possess

targeted to give more competence discharge of anticancer drug. In this work, bis-demethoxy

CUR equivalent loaded chitosan-starch (BDMCA-CS) nano-material components were

arranged using various proportions of CHI and starch by ionic gelation procedure. The

31

entrapment competence, 86.60%, and drug carrying ability, 24.25%, were uppermost for the

synthesis with the ratio 3: 1 of BDMCA: CS. These preparations showed continued discharge

of BDMCA. Then, formulation of BDMCA-CS (3:1) showed anti-cancer behavior in

contradiction of the breast cancer cell lines (MCF- 7). Kinetic approach of drug discharge

pattern exposed that the discharge of BDMCA from the CS nano-materials tracked both

dispersion and polymeric attrition paths. Resultantly, it was observed that the CS nano-

materials are applied as an improved delivery tool for BDMCA to remedy breast cancer

(Subramanian et al., 2014).

Curcumin incorporated dextran sulfate-chitosan NPs were synthesized by simple co-

acervation procedure. Inquiries on frame-up productivity; in vitro drug discharge, cell

approval and cytotoxicity of the synthesized NPs were showed. The NPs have a round

structure with negative zeta ability and high colloidal resistivity. By using this technique the

working efficiency of CUR has been increased as compared to previous reported method, that

is 70% of CUR was discharged after 120 h and the showed drug discharge ratio was good

than previous one. These conclusion propose that dextran sulfate-chitosan NPs are an unique

carrier to transfer hydrophobic drugs like CUR, particularly for treating cancer (Anitha et al.,

2011).

For the treating the dermal wound an in situ injectable N,O-carboxymethyl

chitosan/oxidized alginate nano-materials hydrogel was successfully established for slow in

vitro release of encapsulated nano-curcumin with standardable method (Li et al., 2012). It is a

difficult process of wound healing because the shrinkage and stopping of wound material and

repair of a useful fence. By using inflammation, granulation and remodeling the wound is

repaired that is tissue is regenerated (Merrell et al. 2009). For treatment of wound tissues the

natural materials are to be used, such as since 1980s, are hyaluronic acid (HA), and CHI. The

reported works cleared that by using the nano-technology the fruitful outcomes are come

before researcher regarding to wound healing tissue problems especially by using rat as

experimental specimens. The combination of nano CUR and N,O carboxymethyl

chitosan/oxidized alginate hydrogel in the presence of protein, DNA, and hydroxyproline

gratified in wound skin site focused that could significantly enhanced the development of

wound treating (Li et al., 2012).

In situ induced CS-based water gel contained of chitosan, genipin and salt of sodium

by the linking that is chemically or physically (Titima et al., 2015). In vitro CUR discharge

32

curriculum presented stable discharge of CUR more than other reported system. These

hydrogels confirmed their ability as CUR carrying tempelate.

2.4.5 Protein/curcumin-chitosan nanosuspension

Kafirin-blended NPs to do protect transfer of bio energetic materials because it is poor loving

to help GI tract environs. Inspit of it CUR act as good capsulated material for carry the

proteinic substances accordingly due to better affinity like H-bonding (Taylor et al., 2009).

In addition, The solubility of CUR has been increased than pristine CUR by complexation

with kaf, particularly for oral transfer. Masses of the soluble complex were afterward

prepared due to non aquous connections between the bound CUR materials. The value was

dictated by the hydrophobicity of CUR and kaf nanoplex was due to complex collections later

segregated out to prepare the CUR–kaf nanoplex upon attainment a serious collective

absorption, whose the strong electrostatic interfaces between CUR and kaf particles repressed

the later from collecting into arranged ordered morphology among precipitation, resultant in

the preparation of disorder CUR–kaf nanoplex. Higher solubility of CUR-kaf complex in

aqueous solution focused to more interface between chitosan (positively charged) and CUR-

kaf (negatively charged) complex bring about in more filling addition in nanoparticles. The

combination of CM-chitosan enhances the overall tempelating and adding competence of cc-

kaf from 55% to 86% and 5% to 6.1% that may be qualified to catching of pristine CUR by

self-accumulation of CM chitosan components in solution, or CM-chitosan supported

entrapted surface CUR in kaf nano-materials. While comparing the properties of pristine

CUR and blended CUR regarding to UV light stability, it is cleared that in blends form CUR

showed more stability. If we treated at about 60 min of CUR-kaf and CUR-kaf/CMC

suspensions and pristine suspension there is cleared that in combination form it showed more

stability as compared to native form. At the end of UV treatment, 45% and 50% of CUR was

noted to be remained in CUR-kaf and CUR-kaf/CMC interruption, correspondingly, as

compare to 25% for pristine curcumin solution (Xiao et al., 2015). By doing the same process

in vitro discharge outlines of natural curcumin, CUR-kaf, CUR-kaf/CMC, only 10% of

pristine curcumin was noted at initial 30min of SGF dosing; From this also cleared that

pristine curcumin given passive solubility up to 6 h observation process. This prominently

shows that when observing via the GI area only little group of pristine curcumin near about

13 mg/ ml, which is the soaked dissolution in aqueous phase with 0.5% tween 20, present in

the arrangement of mixed curcumin, which may be efficiently immersed in small intestinal

(Shoba et al., 1998). The kinetic solubility of CUR-kaf and CUR-kaf/CMC presented like

33

biphasic shapes in SGF and SIF. In both combination burst result at starting of every fluid

adding way was noted for both combinations, perhaps due to the fast solubility of incidentally

encapsulated CUR (Xiao et al., 2015).

2.4.6 O-carboxymethyl CHI nanocarrier for curcumin

Due to poor solubility of CHI material its novel behavior became difficult to be come under

use. Therefore it is dire needed to change in chitosan material by physically or chemically to

improve its lacking areas in proper way. If chitosan is combined or blend with carboxymethyl

than the solubility of CHI became better without effect of its other properties. In above

mention substance the process of combination is temperature dependent that is if reaction

carried out at room temperature favors O-substitution, while higher temperature favors N-

substitution (Fernando & Sergio, 2004). The capability of O-CMC as a transporter for water

isoluble drugs in cancer marked drug distribution uses was assessed (Anitha et al., 2011). A

common procedure of solvent evaporation and then ionic gelation was established to develop

a nano blended on O-CMC into which the water insoluble anticancer drug, CUR, was laden

(Figure 2.6). This method strained to solubilize CUR and after this to exit it in O-CMC NPs

having H-bonding relation between the -COOH group of O-CMC and -OH group of CUR

(Anitha et al., 2011). The negative worth of zeta possible showed the constancy of the NPs

system. CUR-OCMC Nps showed no crystal-like peaks when associated to pristine CUR.

The shapeless outline of multifaceted was nominated to intermolecular communication

between O-CMC and CUR within the NPs template. Increasing in both cellular uptake and

cell apoptosis was noted with excessing strength of CUR added in O-CMC nanomaterials

(Anitha et al., 2011).

34

Figure 2.6: Chemical structure of (A) O-CMC, (B) curcumin; (C) Solubility of curcumin

(a) curcumin in water, O-CMC Nps and curcumin-OCMC Nps (Anitha et al., 2011).

2.4.7 Amphiphilic-chitosan microparticles and curcumin

Among CHI derivatives, amphiphilic CHI derivatives are kinds of materials which have

intensively been presented because of fruitful characters. Chitosan substance in its natural

situation has no amphiphilicity. Different amphiphilic CHI byproducts like carboxymethyl

hexanoyl chitosan (Anitha et al., 2011) water soluble N-methylated chitosan possessing

hydrophobic -N(CH3)2, -NH(CH3) and hydrophilic -N-(CH3)3 groups (Sieval et al., 1998) etc.

were proposed to increase the mucoadhesive and dissolution behaviors of CHI.

Spectrophotometric conclusions after the dissolution of CUR and LSCHI-CUR in water

solution reported increasing in solubility and bioavailability of CUR after encapsulation

method (Shelma & Sharma, 2013). Pharmacokinetic determining showed 11.5-fold enhanced

pharmacological obtainability of CUR with encapsulated CUR compared with native CUR

after oral administration in rats (Shelma & Sharma, 2013). In this study (Shelma & Sharma,

2011), hydrophilic and hydrophobic drugs were encapsulated onto the amphiphilic CHI, i.e.,

Lauroyl sulfated chitosan micro particles and its release properties were compared. Curcumin

incorporated dextran sulfate-chitosan were synthesized by simple co-acervation procedure.

Inquiries on frame-up productivity; in vitro drug discharge, cell approval and cytotoxicity of

the synthesized were showed. These have a round structure with negative zeta ability and

high colloidal resistivity. By using this technique the working efficiency of CUR has been

increased as compared to previous reported method, that is 70% of CUR was discharged after

35

120 h and the showed drug discharge ratio was good than previous one. A slow and measured

discharge of CUR in 30 days from the microparticles was perhaps due to the non-water

soluble behavior between CUR and lauroyl groups on CHI. Therefore, it may survive the pre-

mature deprivation of merged drug (Shelma & Sharma, 2011).

2.4.8 Metal Oxide-chitosan nanocomposite for curcumin delivery

Although the chemotherapies and radiotherapies are used to treat cancer, but due to its not

positive results therefore a dire need of nontoxic medicine. The side effects that face a cancer

patient during treatment as fatigue, nausea, insomnia, delirium and vomiting (Savard &

Morin, 2001). O-carboxymethyl chitosan (O-CMCS) based nanocomposites (NCs) with

nanostructured zinc oxide (n-ZnO) were prepared which have effectual water soluble

behavior (Upadhyay et al., 2015). The pictorial representation for the preparation of O-

CMCS/n-ZnO nanocomposites and (i) O-CMCS/n- ZnO/curcumin nanocomposite (ii) is

presented in Figure 2.7.

The electrostatic attachment between ZnO and O-CMCS and curcumin with O-CMCS

in Cr/O-CMCS/n-ZnO NCs was established by FT-IR observation and bare stable structure

given by SEM. The consistent setup and loading ability of curcumin in O-CMCS/n-ZnO

nano-materials are 74% and 43%, which enhanced with quantity of O-CMCS/n-ZnO

nanocomposites that supported standard enhanced in drug adding and catching and enlarged

the particle extent also. A pH reliant on statement retort was noted and is greater in acidic pH

due to protonation of -NH2 groups of CMCS, which really reason bulge of material. Cr

adding into O-CMCS/n-Zn nanocomposites increased the drug dissolution in water. The

anticancer activity of curcumin and Cr/O-CMCS/n-ZnO nanocomposites presented that

curcumin calculated its anticancer behavior into material tempelate after adding and the

anticancer belongings were enhanced in the presence of ZnO (Upadhyay et al., 2015).

36

Figure 2.7: Pictorial representation for O-CMCS/n-ZnO nanocomposites (i) and O-

CMCS/n-ZnO/curcumin nanocomposite (Upadhyay et al., 2015).

2.5 Clay Based Polymer Bio-nanocomposites

Madusanka et al. (2015) reported a new curcumin initiated carboxymethylcellulose–

montmorillonite nanocomposite. Curcumin which is ater insoluble material for which

carboxymethyl cellulose (CMC) was applied as an emulsifier to get antibacterial/anti-cancer

behaviors. For kinetics behavior to gain the montmorillonite (MMT) nanoclay was added in

the making as a materials substance. It was noted that water dissolution ability of CUR in the

nanocomposite has prominently enhanced (60% release within 2 h and 30 min in distilled

water at pH 5.4) associated to pristine CUR. The synthesized CUR blended carboxymethyl

cellulose montmorillonite nanocomposite is good as a CUR transporter having better release

and morphological properties.

Zuber et al. (2010) prepared chitin blended PU bio-nanocomposites (PUBNC) by

emulsion polymerization. A combination of polymeric material and bentonite clay

supplemented in montmorillonite (MMT) was shaped in emulsion polymerization, in which

MMT spread inversely contingent on communication of MMT with polymer materials.

Cation exchange capacity (CEC) of bentonite clay enriched in montmorillonite was found 74

meq/100 g. The being of the inserted clay in PU medium was long-established using optical

37

microscope (OM) technique. Optical microscope (OM) photographs confirmed the well

spread orderly intercalated accumulates sheets of bentonite in PU medium.

Zia et al. (2010) prepared chitin based polyurethane bio-nanocomposites (PUBNC) by

emulsion polymerization. The presence of the added clay by polyurethane (PU) in the

mixture was investigated using X-ray diffraction (XRD), dynamic mechanical measurements

and optical microscope (OM) techniques. The values of enthalpies changes (DH) concerned

with various bentonite nanoclay quantity are more reliable with the crystalline outline of the

prepared PUBNC sheets. From these observation it is cleared that pure silicate vanish in

PU/bentonite nanoclay mixture and a set of new peaks show conforming to the basal layout

of PU/bentonite clay bio-nanocomposites. The values of tan δ versus temperature was also

noted using dynamic mechanical measurements were compatible with crystalline design of

the PUBNC samples.

In this review literature chapter, the PU and PU based materials, curcumin and curcumin

based materials, chitin/chitosan based materials , chitosan-curcumin based materials and clay

based polymer bio-nanocomposite materials work of different researchers were reported.

From the reported work it is cleared that PUs and PUs based materials are sectioned PUs,

having of hard and soft sections are confirmed to have microphase discrete morphology,

which able it to be applied in different scenario such as glues, coatings, biomedical

substances and elastomers. PUEs due to their biocompatible properties are considered as

unique polymer (Zia et al., 2009). Typical applications include blood-contact materials, heart

valves (Hoffman et al., 1993), and insulators for pacemaker, electrical leads, cardiovascular

catheters and implants for the knee joint meniscus (Klompmaker et al., 1993). Curcumin and

curcumin based materials has also been exposed to have important vitro antioxidant, diabetic

complication, antimicrobial agent, neuroprotective, anti-cancer, antithyroid cancer cells,

detection of hypochlorous acid, wound healing, treatment of major depression. For treating

the human being diseases in India curcumin is used for recovering from harmful problems

such as disorders, cough, diabetic ulcers etc. According to researcher the combination of

curcumin cream with lime may be used for treating wounds and inflammation as a home

remedy (Anamika, 2012). Chitin based substances are favored applicants for surgical

filaments with ongoing inquiries into their in vitro biocompatibility and non-toxicity. But by

changing the trend the uses of chitin and its derivative have also been changed according to

latest requirement i.e, for cosmetic, medical, pharmaceutical and biotechnological use (Kurita

et al., 1986). In vitro biocompatibility and cytotoxicity of chitin/BDO blends based PU

38

elastomers have also been studied in the literature. Chitosan-curcumin based materials hasten

wound covering, enhance DNA and protein amount, give better mucoadhesion, surviving

cancer causing HT-29, SCC25, Caco-2 cell lines by apoptosis and capturing the cell circle.

Pharmacokinetic study of CUR loaded CS blend drug distribution scheme confirms an

protracted therapeutic era, passive enhance and continued plasma strength of CUR, delays

drug passes duration in vivo with lower Ke and longer T1/2, survive it from damaging,

enhance dissolution and picking, standard flows and stable discharge of CUR, increases AUC

worth of CUR after oral management, shimmering an improved bioavailability. The NPs of

this mucoadhesive material (chitosan) relate with the negatively exciting mucosal superficial

and can be helpful to increase the interaction time of drug distribution scheme in the mucosa,

which could enhance the therapeutic working of CUR or/and other drugs (Mazzarino et al.,

2012). The CUR stimulated carboxymethyl cellulose–montmoriilonite nanocomposite is an

active curcumin transporter with increased solid state characters. It also has profitable ability

provide that three parts are harmless and pharmaceutically recognized and inexpensive. The

solid merged substance is even under room temperature and can be frequently pellatised to

give tablets (Madusanka et al., 2015). Polymer nanocomposite is a period of mixture

substances collected of an organic polymer medium with spread inorganic nanofillers, which

have as a minimum one dimension in nanometer array (Giannelis, 1996).

39

Chapter 3

MATERIALS AND METHODS

This research work was completed at Department of Applied Chemistry, GC University

Faisalabad, Pakistan. The present research work was divided into seven parts, in which the

behavior of polyurethane was studied by using seven different aspects. The detailed

discussion of are described below.

(a): Synthesis and characterization of novel curcumin based polyurethanes varying

diisocyanate structure.

(b): Synthesis, structural, thermal and surface characterization of chitin/curcumin/BDO

blends based polyurethane elastomers.

(c): Synthesis, structural, thermal and surface characterization of curcumin/BDO blends

based polyurethane elastomers.

(d): Synthesis, structural, thermal and surface characterization of chitin/curcumin blends

based polyurethane elastomers.

(e): Synthesis, structural, thermal and surface characterization of chitin/clay,

curcumin/clay and BDO/clay based polyurethane elastomers and bio-

nanocomposites.

(f): Synthesis, structural, thermal and surface characterization of chitin/curcumin/BDO

and chitin/curcumin/BDO/clay blends based polyurethane elastomers and bio-

nanocomposites.

(g): Synthesis, structural, thermal and surface characterization of curcumin/BDO and

curcumin/BDO/clay blends based polyurethane elastomers and bio-nanocomposites.

(h): Synthesis, structural, thermal and surface characterization of chitin/curcumin and

chitin/curcumin/clay blends based polyurethane elastomers and bio-nanocomposites.

40

3.1 Chemicals/Apparatus

Chemical and apparatus used for the above mention studies are given below

3.1.1 Chemicals

Chitin was purchased from the Iran Polymer and Petrochemical Institute (Tehran, I.R. Iran).

The M.W of chitin was realized according to recommended procedure available in literature

(Chen et al., 2002). The purification of chitin was done by recommended method (Wang et

al., 1991). The required amount was treated in 0.5 wt % aqueous potassium permanganate

(Merck) solution up to 1 h and after this washed with distilled water. Then in 1 wt% aqueous

oxalic acid (Merck) solution, chitin was treated for 20 min at 30 °C, after this it was washed

and dried. Curcumin, HTPB, HMDI, Methylene bis(p-cyclohexyl isocyanate) (H12MDI),

Isophorone diisocyanate(IPDI), Toluene diisocyanate (TDI), Methylene diphenyl

diisocyanate (MDI) 1,4-butane diol (BDO) were bought from Sigma–Aldrich Chemical Co.

BDO also treated in order to remove air bubble at 80 °C under vacuum for 24 h. HMDI and

all other substances were applied as purchased. All the substances applied in this work were

on standard. The subsequent chemicals were applied acoordigly without any further

treatment. Hydroxy-terminated polybutadiene (HTPB), hexamethylene diisocyanate

(HMDI), Hydrogen peroxide, Dimethyl Sulfoxide (DMSO), Acetone, Distilled water,

Potassium hydroxide, Pyrogallol, Paraffin oil, Nitrogen gas and Grease.

3.1.2 Apparatus

Following apparatus are used during the research work:

Four- necked round bottom flask, Pipette, Beaker, Heating oil bath, Dropping funnel,

Thermometer, Reflux condenser, Analytical balance, Electrical oven, Mechanical stirrer, Hot

plate, Magnet, Measuring cylinder, Nitrogen gas cylinder, Teflon plate, Spatula of steel,

Aluminium foil, Wolf bottle (two necked at sides) and Stand.

41

3.2 Synthesis of Novel Curcumin Based Polyurethanes Varying

Diisocyanate Structure

3.2.1 Synthesis of polyurethane

The sample was prepared by following two steps. In first step prepolymer was formed by the

reacting of hydroxyl terminated polybutadiene (HTPB) and Hexamethylene diisocyanate

(HMDI), while in second step by using chain extender the final polymer was formed.

According to Zia et al. (2008) method prepolymer was prepared by using 3 mole of

diisocyanate and 1 mole of diol to get NCO ended prepolymer. Polyol (HTPB) was placed in

four-necked retort flask furnished with machine-driven stirrer, warming oil bath, reflux

condenser, and N2 inlet and outlet system. Oil bath temperature was augmented up to 60 ºC,

after this by increasing temperature up to 100 ºC HMDI was added. According to optimum

standard, the process of formation of prepolymer was completed in 1 h scheme 3.1. The

catalyst was added before addition of chain extenders. The PU prepolymer elastomers were

transformed into final polymer by adding BDO, curcumin with unceasing stirrer at 100 °C.

The process of stirring was continued until the homogeneity in reactant mixture was obtained

that signifies the completion of reaction and then fabricated in to uniform layer of thickness

2-3 mm by casting on Teflon plate. The prepared polymer samples were cured at 100 °C for

24 hour in retort oven. After curing the synthesized polymer materials were kept at room

temperature prior to further analysis. The complete preparation designs are presented in Table

3.1. The diagrammatic reaction path for the preparation of curcumin, 1,4-butanediol centered

polyurethane elastomers are presented in Schemes 3.1.

42

OCN

NCOHC CH CH2H2C OHO H

n

+

HMDI HTPB

HC CH CH2H2C OO C

n

NH

O

CH2 NCO

6

CHN

O

H2COCN

6

NCO terminated PU prepolymer

OCH3

OH

H3CO

HO

O O

Curcumin

HOOH

1,4-butanediol

HC CH CH2H2C OO C

n

NH

O

CH2 NH

6

CHN

O

H2CHN

6

H3CO

O

OCH3

O

OO

C O CO

OH2CO

4m

O

O

H3CO

HO

CH3

H

O OH

(a) HMDI-HTPB-BDO-Cur based PU

CH2 NCOOCN

H12 MDI

+ HC CH CH2H2C OHO H

n

HTPB

HC CH CH2H2C OO C

n

CH2 NCONHCCH2

HNOCN

O O

NCO terminated PU prepolymer

OCH3

OH

H3CO

HO

O O

Curcumin

HOOH

1,4-butanediol

43

HC CH CH2H2C OO C

n

CH2 NHNHCCH2

HNHN

O O

H3CO

O

OCH3

O

OO

C O CO

OH2CO

4m

OH

(b) H12MDI-HTPB-BDO-Curcumin based PU

Curcumin

+HC CH CH2H2C OHO H

n

HTPB

NCO

NCO

IPDI

HC CH CH2H2C OO C

n

NCO

HN

O

C

O

NH

NCO NCO terminated PU prepolymer

OCH3

OH

H3CO

HO

O O

Curcumin

HOOH

1,4-butanediol

HC CH CH2H2C OO C

n

NH

HN

O

C

O

NH

NH

H3CO

O

OCH3

O

OO

C

O

C

OH2CO

4

O

m

(c) IPDI-HTPB-BDO-Curcumin based PU

OH Curcumin

44

OCH3

OH

H3CO

HO

O O

Curcumin

HOOH

1,4-butanediol

NCO terminated TDI based prepolymer

CH3

HN

NH

HC CH CH2H2C OO C

n

CH3

NH

NH

C

O O

H3CO

O

OCH3

O

OO

C C

OH2CO4

O O

m

OH Curcumin

(d) TDI-HTPB-BDO-Curcumin based PU

OCH3

OH

H3CO

HO

O O

Curcumin

HOOH

1,4-butanediol

NCO terminated MDI based prepolymer

CH2 NHHNCH2 NHNH HC CH CH2H2C OO C

O

C

O

n

C O

H3CO

O

OCH3

O

OO

C

O

O

H2CO

4m

(e) MDI-HTPB-BDO-Curcumin based PU

OH Curcumin

Scheme 3.1 Synthetic route for the synthesis of: (a) HMDI-HTPB-BDO-Curcumin

based polyurethane (IPU1); (b) H12MDI-HTPB-BDO-Curcumin based polyurethane

(IPU2); (c) IPDI-HTPB-BDO-Curcumin based polyurethane (IPU3); (d) TDI-HTPB-

BDO-Curcumin based polyurethane (IPU4); (e) MDI-HTPB-BDO-Curcumin based

polyurethane (IPU5).

45

Table 3.1 Formulation ratio of different raw materials used in the synthesis of

polyurethanes extended with blends of curcumin/1,4-butane diol

Sr.

No.

Sample code Diisocyanate

(variables)

Diisocyanate

(moles)

HTPBf

(mole)

BDOg

(mole)

Curcumin

(mole)

1 IPU1 HMDIa

3 1 1 1

2 IPU2 H12MDIb

3 1 1 1

3 IPU3 IPDIc

3 1 1 1

4 IPU4 TDId

3 1 1 1

5 IPU5 MDIe

3 1 1 1

aHexamethylene diisocyanate (HMDI)

bMethylene bis(p-cyclohexyl isocyanate) (H12MDI)

cIsophorone diisocyanate(IPDI)

dToluene diisocyanate (TDI)

eMethylene diphenyl diisocyanate (MDI)

fHydroxy terminated poly butadiene (HTPB)

g1,4-butane diol

46

3.3 Synthesis of Chitin / Curcumin / BDO / clay Blends Based Polyurethane

Elastomers and Bio-nanocomposites

The sample was prepared by following two steps. In first step prepolymer was formed by the

reacting of hydroxyl terminated polybutadiene (HTPB) and Hexamethylene diisocyanate

(HMDI), while in second step by using chain extender the final polymer was formed.

Preparation of PU prepolymer elastomer and bio-nanocomposite

The prepolymer elastomer was prepared by established method (Zia et al., 2008) and

prepolymer bio-nanocomposite was synthesized by recommended procedure (Zuber et al.,

2010). According to Zia et al. (2008) method prepolymer was prepared by using 3 mole of

diisocyanate and 1 mole of diol to get NCO ended prepolymer. Polyol (HTPB) was placed in

four-necked retort flask furnished with machine-driven stirrer, warming oil bath, reflux

condenser, and N2 inlet and outlet system. Oil bath temperature was augmented up to 60 ºC,

after this by increasing temperature up to 100 ºC HMDI was added. According to optimum

standard, the process of formation of prepolymer was completed in 1 h (Scheme 3.2). Further

confirmation was done by taking the FTIR spectrum of NCO terminated prepolymer (Figure

4.5a). Following the procedure of Zuber et al. (2010) weighed mentioned amount of clay

(Table 3.5) was completely homogenized with solvent dimethyl sulfoxide (DMSO), after this

the clay/solvent mixture was homogenized with polyol for 1h. This homogenized polyol and

clay material were reacted with HMDI at 90-95 °C to obtain NCO terminated prepolymer bio-

nanocomposites (Scheme 3.5) by using same method as earlier discussed in (Zia et al., 2008).

Further confirmation was done by taking the FTIR spectrum of NCO terminated prepolymer

bio-nanocomposite (Figure 4.27a).

3.3.1 Preparation of polyurethane elastomers and bio-nanocomposites

The PU prepolymer elastomers and bio-nanocomosites were transformed into final polymer

by adding pristine BDO, curcumin, chitin or mixtures of curcumin/BDO/chitin with

unceasing stirrer at 100 °C. The process of stirring was continued until the homogeneity in

reactant mixture was obtained that signifies the completion of reaction and then fabricated in

to uniform layer of thickness 2-3 mm by casting on Teflon plate. The prepared polymer

samples were cured at 100 °C for 24 hour in retort oven. After curing the synthesized polymer

materials were kept at room temperature prior to further analysis. The complete preparation

designs are presented in Tables 3.2, 3.3, 3.4, 3.5, 3.6, 3.7 and 3.8. The diagrammatic reaction

47

path for the preparation of chitin, curcumin, 1,4-butanediol and clay centered polyurethane

elastomers and bionanocomposites are presented in Schemes 3.2, 3.3, 3.4, 3.5, 3.6, 3.7 and

3.8.

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6

Hydroxy terminated polybutadiene (HTPB) Hexamethylene diisocyanate (HMDI)

Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO- Terminated polyurethane prepolymer

H2CH2C

H2C

H2C OHHO

1,4-Butane diol

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

C

O

O

CO

OH2C O

4

p

3.2a-1,4-butane diol based polyurethanes

48

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n


OCH3

OH

H3CO

HO

O O

Curcumin

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

H3CO

O

OCH3

O

OO

C O

O

CO

p

OH Curcumin

3.2b-Curcumin based polyurethanes

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n


OHH

NHCOCH3H

OH

CH2OH

HO

HH

NHCOCH3H

OH

CH2OH

HO O

n

Chitin

49

OHH

NHCOCH3H

OH

H2C

HO

HH

NHCOCH3H

OH

CH2OH

HO O

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n C O

O

CO

O

p

3.2c-Chitin based polyurethanes

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n


OCH3

OH

H3CO

HO

O O

Curcumin

O

NHCOCH3

OH

CH2OHO

NHCOCH3

OH

CH2OH

OO

OCH2OH

NHCOCH3H

OH O

n

Chitin

H2CH2C

H2C

H2C OHHO

1,4-Butane diol

50

HC CH CH2H2C OO Cn

O

NH CH2NH

6C

O

HNH2CHN6

m C O

O

CO

O

OHH

NHCOCH3H

OH

CH2

HO

HH

NHCOCH3H

OH

CH2OH

HO O

O

O

H3CO

HO

OCH3

OH

O

O

O OCH3

H

CH3

H

HO O

H

OH Curcumin

(CH2)4

O

p

3.2d-Curcumin, Chitin and BDO based polyurethanes

Scheme 3.2 (a) Reaction scheme for KPU1 (polyurethane extended with 1.4-BDO (b)

Reaction scheme for KPU2 (polyurethane extended with curcumin); (c) Reaction

scheme for KPU3 (polyurethane extended with chitin); (d) Reaction scheme for KPU4-

KPU6 (polyurethanes extended with curcumin/chitin/BDO).

51

Table 3.2: Sample code designation and various constitutions of BDO/curcumin/chitin

established polyurethane elastomers

Sr.

No.

Sample

symbol

Formation (%)

BDOa/curcumin/chitin

Molar proportion of

HTPBb/HMDI

c/BDO/Curcumin/chitin

1 KPU1 100/0/0 1:3:2:0:0

2 KPU2 0/100/0 1:3:0:2:0

3 KPU3 0/0/100 1:3:0:0:2

4 KPU4 50/25/25 1:3:1:0.5:0.5

5 KPU5 25/50/25 1:3:0.5:1:0.5

6 KPU6 25/25/50 1:3:0.5:0.5:1

a1,4-butane diol

bHydroxy terminated poly butadiene (HTPB)

cHexamethylene diisocyanate (HMDI)

52

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6


Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO terminated polyurethane prepolymer

H2CH2C

H2C

H2C OHHO

1,4-Butane diol

OCH3

OH

H3CO

HO

O O

Curcumin

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

H3CO

O

OCH3

O

OO

C OCO O

CH2

O

4

p

OH Curcumin

Scheme 3.3 Curcumin and BDO blends based polyurethane elastomers

53

Table 3.3: Sample code designation and different formulation of BDO/curcumin based


Sr# Sample code Composition (%)

BDOa/curcumin

Molar ratio of

HTPBb/HMDI

c/BDO/Curcumin

1 KPU1 100/0 1:3:2:0

2 KPU2 0/100 1:3:0:2

3 KPU7 75/25 1:3:1.5:0.5

4 KPU8 50/50 1:3:1:1

5 KPU9 25/75 1:3:0.5:1.5

a1,4-butane diol



54

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6


Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n


OHH

NHCOCH3H

OH

CH2OH

HO

HH

NHCOCH3H

OH

CH2OH

HO O

n

Chitin

OCH3

OH

H3CO

HO

O O

Curcumin

HC CH CH2H2C OO Cn

O

NH CH2NH

6C

O

HNH2CHN6

m C O

O

CO

O

p

OHH

NHCOCH3H

OH

CH2

HO

HH

NHCOCH3H

OH

CH2OH

HO O

OCH3

OH

O

O

O OCH3

H

H

OH Curcumin

Scheme 3.4 Chitin/curcumin blends based polyurethane elastomers

55

Table 3.4: Sample code designation and different formulation of curcumin/chitin based



curcumin/chitin

Molar ratio of

HTPBa/HMDI

b/Curcumin/chitin

1 KPU2 100/0 1:3:2:0

2 KPU3 0/100 1:3:0:2

3 KPU10 75/25 1:3:1.5:0.5

4 KPU11 50/50 1:3:1:1

5 KPU12 25/75 1:3:0.5:1.5

aHydroxy terminated poly butadiene (HTPB)

bHexamethylene diisocyanate (HMDI)

56

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6 + Clay +

S

O

H3C CH3

Hydroxy terminated polybutadiene Hexamethylene diisocyanate DMSO

Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO- Terminated clay based polyurethane prepolymer bio-nanocomposite

H2CH2C

H2C

H2C OHHO

1,4-Butane diol

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

C

O

O

CO

OH2C O

4

p

3.5 a-1,4-butane diol/clay based polyurethane bio-nanocomposite

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

57


OCH3

OH

H3CO

HO

O O

Curcumin

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

H3CO

O

OCH3

O

OO

C O

O

CO

p

OH Curcumin

3.5 b-Curcumin/clay based polyurethane bio-nanocomposite

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO- Terminated clay based polyurethane prepolymer

OHH

NHCOCH3H

OH

CH2OH

HO

HH

NHCOCH3H

OH

CH2OH

HO O

n

Chitin

58

OHH

NHCOCH3H

OH

H2C

HO

HH

NHCOCH3H

OH

CH2OH

HO O

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n C O

O

CO

O

p

3.5 c-Chitin/clay based polyurethane bio-nanocomposite

Scheme 3.5 (a) Reaction scheme for KPU1-clay (polyurethane extended with 1.4-

BDO/clay (b) Reaction scheme for KPU2 (polyurethane extended with curcumin/clay);

(c) Reaction scheme for KPU3 (polyurethane extended with chitin/clay).

59

Table 3.5: Sample code designation and different formulation of

BDO/curcumin/chitin/clay based polyurethane elastomers and bio-nanocomposites

Sr# Sample

code

Composition (%)

BDOa/curcumin/chitin/clay

Molar ratio of

HTPBb/HMDI

c/BDO/Curcumin/chitin/clay

1 KPU1 100/0/0/0 1:3:2:0:0:0

2 KPU1-clay 100/0/0/0.1 1:3:2:0:0:0.1

3 KPU2 0/100/0/0 1:3:0:2:0:0

4 KPU2-clay 0/100/0/0.1 1:3:0:2:0:0.1

5 KPU3 0/0/100/0 1:3:0:0:2:0

6 KPU3-clay 0/0/100/0.1 1:3:0:0:2:0.1

a1,4-butane diol



60

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6 + Clay +

S

O

H3C CH3


Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO- Terminated clay based polyurethane prepolymer biocomosite

OCH3

OH

H3CO

HO

O O

Curcumin

O

NHCOCH3

OH

CH2OHO

NHCOCH3

OH

CH2OH

OO

OCH2OH

NHCOCH3H

OH O

n

Chitin

H2CH2C

H2C

H2C OHHO

1,4-Butane diol

HC CH CH2H2C OO Cn

O

NH CH2NH

6C

O

HNH2CHN6

m C O

O

CO

O

OHH

NHCOCH3H

OH

CH2

HO

HH

NHCOCH3H

OH

CH2OH

HO O

O

O

H3CO

HO

OCH3

OH

O

O

O OCH3

H

CH3

H

HO O

H

OH Curcumin

(CH2)4

O

p

Scheme 3.6 Curcumin, Chitin, BDO and clay based polyurethane bio-nanocomposites

61

Table 3.6: Sample code designation and different formulation of BDO / curcumin /

chitin / clay based polyurethane elastomers and bio-nanocomposites.

Sr# Sample

code

Composition (%)

BDOa/curcumin/chitin/clay

Molar ratio of

HTPBb/HMDI

c/BDO/Curcumin/chitin/clay

1 KPU4 50/25/25/0 1:3:1:0.5:0.5:0

2 KPU4-clay 50/25/25/0.1 1:3:1:0.5:0.5:0.1

3 KPU5 25/50/25/0 1:3:0.5:1:0.5:0

4 KPU5-clay 25/50/25/0.1 1:3:0.5:1:0.5:0.1

5 KPU6 25/25/50/0 1:3:0.5:0.5:1:0

6 KPU6-clay 25/25/50/0.1 1:3:0.5:0.5:1:0.1

a1,4-butane diol



62

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6 + Clay +

S

O

H3C CH3


Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n


H2CH2C

H2C

H2

C OHHO

1,4-Butane diol

OCH3

OH

H3CO

HO

O O

Curcumin

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NH

6

H2

CHN

6 m

n

H3CO

O

OCH3

O

OO

C OCO O

CH2

O

4

p

OH Curcumin

Scheme 3.7 Curcumin, BDO and clay based polyurethane bio-nanocomposites

63

Table 3.7: Sample code designation and different formulation of BDO/curcumin/clay

based polyurethane elastomers and bio-nanocomposites.


BDOa/curcumin/clay

Molar ratio of

HTPBb/HMDI

c/BDO/Curcumin/clay%

1 KPU7 75/25/0 1:3:1.5:0.5:0

2 KPU7-clay 75/25/0.1 1:3:1.5:0.5:0.1

3 KPU8 50/50/0 1:3:1:1:0

4 KPU8-clay 50/50/0.1 1:3:1:1:0.1

5 KPU9 25/75/0 1:3:0.5:1.5:0

6 KPU9-clay 25/75/0.1 1:3:0.5:1.5:0.1

a1,4-butane diol



64

CH

CH

H2C

H2C OHOH

n +

H2

COCN NCO

6 + Clay +

S

O

H3C CH3


Time 1 hr90-100 °C

CH

CH

H2C

H2C OOC C

O

NH

O

HNH2

C NCO

6

H2

COCN

6 m

n

NCO- Terminated clay based polyurethane prepolymer

OHH

NHCOCH3H

OH

CH2OH

HO

HH

NHCOCH3H

OH

CH2OH

HO O

n

Chitin

OCH3

OH

H3CO

HO

O O

Curcumin

HC CH CH2H2C OO Cn

O

NH CH2NH

6C

O

HNH2CHN6

m C O

O

CO

O

p

OHH

NHCOCH3H

OH

CH2

HO

HH

NHCOCH3H

OH

CH2OH

HO O

OCH3

OH

O

O

O OCH3

H

H

OH Curcumin

Scheme 3.8 Chitin/curcumin/clay based polyurethane bio-nanocomposites

65

Table 3.8: Sample code designation and different formulation of curcumin/chitin/clay

based polyurethane elastomers and bio-nanocomposites.


curcumin/chitin/clay

Molar ratio of

HTPBa/HMDI

b/Curcumin/chitin/clay%

1 KPU10 75/25/0 1:3:1.5:0.5:0

2 KPU10-clay 75/25/0.1 1:3:1.5:0.5:0.1

3 KPU11 50/50/0 1:3:1:1:0

4 KPU11-clay 50/50/0.1 1:3:1:1:0.1

5 KPU12 25/75/0 1:3:0.5:1.5:0

6 KPU12-clay 25/75/0.1 1:3:0.5:1.5:0.1

aHydroxy terminated poly butadiene (HTPB)

bHexamethylene diisocyanate (HMDI)

66

3.4 Characterization

The synthesized chitin/curcumin/BDO and chitin/curcumin/BDO/clay based polyurethane

elastomer and composite samples were characterized by applying the different analytical

approaches.

3.4.1 Structural/Morphological characterization

3.4.1.1 Fourier transforms infrared (FTIR) spectroscopy

Fourier transform infrared (FTIR) is a significant and common method to evaluate the

chemical morphology, chain direction and arrangement of various compounds which may

be organic, inorganic and polymeric in nature (Smith, 1996). By using Fourier transform

infra-red (FTIR) spectrometer the spectra of tinny sheets were obtained in the transmission

mode. A Thermo Scientific FTIR was active to observe the functional group of chitin

based polyurethane samples. The scan variety was from 4000 to 500 cm-1

. For this

determination, the films of the products were casted on glass plates and dried in open air.

The structure of the polymeric and non-polymeric substance can be known by using IR

technique. An IR spectrum form many absorption bands that associate to various vibration

modes of the bonds current in the molecule. In any molecule such type of vibrations can

happen but their frequencies must be unlike.

3.4.1.2 Solid state NMR

Solid-state NMR (SSNMR) spectroscopy is a kind of nuclear magnetic resonance (NMR)

spectroscopy characterized by the presence of anisotropic (directionally dependent)

interactions. In solution NMR, spectrum consists of a series of very sharp transitions, due to

averaging of anisotropic NMR interactions by rapid random tumbling. By contrast, solid-state

NMR spectrum is very broad, as the full effects of anisotropic or orientation-dependent

interactions are observed in the spectrum.

3.4.1.3 Scanning electron microscope (SEM)

Characterization of the cellular-structure of chitin based polyurethane was done by using a

6490 (LA) FE-SEM. This method gives evidence about the cell sizes, cell size delivery,

and strut breadth of the chitin based PU. Inspite of it also discloses the anisotropy in the

cellular morphology of slabstock polyurethane samples which blows under free

circumstances and result in cells which are extended along the blow or rise way

67

(Herrington & Hock, 1998). To synthesis samples for the SEM, they were first stable with

Karnovsky's fixative and then occupied through a graded alcohol dryness series. Once

dehydrated, the specimens were placed in a critical point dryer (left image), mounted and

located in a gold coater (center image). Once gold coating was completed, specimens were

viewed on the SEM. Images were scanned on a digital imaging system by computer

enhancement (right image) or polaroid pictures were taken using an attached camera.

Figure 3.1: Scanning electron microscopy technique

3.4.2 X-ray diffractometry (XRD)

In X-ray scattering experiments, a sample is treated with X-rays, and the subsequent

scattering pattern is noted giving to the strength of the dispersed radiation as a resolution of

the scattering angle θ and explained by difference in electron density. Small-angle X-ray

scattering (SAXS) is classically used to show the microstructures oscillating from tens to

thousands of angstrom (Ǻ), defining the phase parting in block polymers. While wide-angle

X-ray scattering is applied to know the crystalline pattern of the solids at atomic level. A

typical X-ray diffractogram (XRD) elucidated the crystalline character of polymer by image

68

from the different crystalline planes in the sample. These reflections are noted at various

angles according to subsequent equation:

Braggs law: 2d sinθ = nλ (3.1)

Where d is the intermission between crystalline planes, θ is the angle that X-ray stream

makes with the planes, λ is the wavelength of the X-ray stream and n is an integer. As the

crystalline segment of the polymers have random alignment and show the same scattering in

all the guidelines. So a one dimensional slice is performed to regulate the scattering pattern. It

is a distinguishing feature of XRD patterns of semicrystlline polymers that the reflexes look

on the top of an amorphous halo (Braun et al., 2005).

3.4.3 Thermal Analysis

3.4.3.1 Differential scanning calorimetry (DSC)

DSC studies thermal change happening in polymeric materials samples when they are

chilled down or animated up under sluggish atmosphere. By using this technique the

melting (Tm) and glass transition (Tg) temperatures can be evaluated also the different

changes in fluid crystal-like mesophase. Two pans are used in parallel form by observing

the heat flow in a typical DSC experiment. In both pans analysis in one pan contains

standard sample and other contain prepared sample for comparative study. After setting

both are heated at specific rate. Now changing the temperature the heat flow rate of both

samples difference is noted. If there is no changing in phases of polymer the graph line is

according to X-axis and heat flow in the form of heat q is noted (Hunt, 1992). In the DSC

the (Tg) temperature is that temperature in which substances are in elastomeric form that is

below it substance is in glassy state and above it in rubbery state, this polymer behaves like

hard glass. From this temperature many informations are obtained such as chemistry of

substances, and about the structures of substances, and also crystallization behavior is also

determined. The most greater temperature in DSC curves are crystalline temperature, at

this stage the polymer is heated further it absorbs further heat and melting temperature is

noted. Amorphous polymers do not display crystallization and melting mountains but a

glass transition. The Tg, Tc and Tm are powerfully needy on the thermal history of the

example. Therefore, several DSC thermal cycles are carried out to scan the thermal

transitions usually in the second and not in the first heating run after a defined cooling

cycle. Moreover, the crystallinity of polymer samples can be measured using DSC

69

technique. In this study DSC analysis was performed to determine the thermal changes of

polyurethanes elastomers by using a Perkin Elmer DSC Diamond series, USA. The

samples were weighed carefully and thermally analyzed in hermetic conditions up to 50-

500 ºC using liquid nitrogen at a heating rate of 10

ºC/min.

3.4.3.2 Thermogravimetric analysis (TGA)

Thermogravimetry (TG) is one of the thermo analytical methods and has been applied

lengthily in the study of organic, inorganic also for polymeric substances. From the

thermogram curves the change in degradation of temperature is noted. This technique is

used to determine the weight loss by increasing temperature is noted. TGA has extensively

been applied in current years, because of the marketable obtainability of automatic and

unceasingly recording thermobalances. Their consequences are very dependable and

precise. The first thermobalance was conceived by P. Chevenard in 1944. A modern

thermobalance is contained on a footage balance, a furnace, controller and computer based

copy device. TGA has two types such as dynamic TGA and static TGA which are done

over the array from 30° to a maximum of 2000°C. The outcomes of TGA is presented in

the practice of arcs and the figure of TGA curves chiefly be contingent on some issues

such as warming rate, geometry of the sample pan, and furnace condition. Also the sample

properties such as weight, element size, nature and stuffing of the example can touch the

TG curves. The sample form can be in the range of 1-150 mg. For precise consequences

sample mass about 25 mg are ideal, but often 1 mg of pulverized substances give

outstanding outcomes. It is a standard method applied to observe the thermal degradation

kinetics of substances such as polymers and elastomers, hence gives evidence about their

thermal solidity as well as shelf life.

3.4.4 Antimicrobial activity test

The antibacterial activity of synthesized polyurethane samples was determined according

to recommended method, agar diffusion method that is available in literature (Pelczar et

al., 1990). According to this method first of all Prepared media Nutrient agar by using

quantity 4.2g/150 mL then it was treated in autoclave at temperature 121˚C upto 15 minute

for dissolving after dissolving it was cooled down to room temperature then injected 10 µL

microbes into the media that present in the flask. Next the prepared media was poured in

large Petri dish and keep it to solidify. Cut the small pieces of prepared polymer and put it

in media prepared petri dish according to their arranged numbers that is IPU1, IPU2, IPU3,

70

IPU4 and IPU5. The plate was incubated at 37 ˚C for 24 h, a growth free „„zone of

inhibition” around the samples were appeared, these zones of inhibition were measured.

3.4.5 Surface characteristics

The surface behaviors such as water absorption and degree of swelling was also be

observed and deliberated, by subsequent the procedure obtainable in the literature (Zia et

al., 2008).

3.4.5.1 Evaluation of water absorption

By evaluating the amount of water that polymer was absorbed, we can calculate the bulk

water loving of the polyurethane. After piecing the samples of size (10 × 10 × 1 mm) were

put in 100 ml Erlenmeyer flasks, possess distill water and kept for 1, 2, 3, 4, 5, 6, and 7

days in treating chamber at 37 ˚C. After every 24 hours the specimens were separated from

water, dried normally with filter paper and measured with balance. The vary in weight of

samples by water uptake was noted.

3.4.5.2 Equilibrium degree of swelling

The equilibrium degree of swelling of prepared polyurethane samples were determined by

dipping small samples of size (20 × 20 × 2 mm3) in DMSO at room temperature for seven

days, then after freshening with paper towel reweigh it again. The degree of swelling was

calculated by following relations:

Where 1/VR is the equilibrium degree of swelling, vR is the volume fraction of elastomer

material in the swollen sample, vS is the volume fraction of solvent in the swollen sample,

ρR is the density of dry sample before treating and ρS is the density of solvent.

3.4.6 Statistical analysis

The results of various analytical parameters were statistically analyzed by computing

respective averages and standard errors (Steel et al., 1997).

1

VR

=vR + vS

vR

= 1 + ρ S

ρ R

× ω S ω

R= 1 +

ρ

ρ S

R ×

ω S+R - ω R ω R

71

Chapter 4

RESULTS AND DISCUSSION

The present research work was performed to study the effect of chain extenders i.e. curcumin,

chitin and 1,4-butanediol (BDO) on the properties of polyurethane by using hydroxyl

terminated polybutadiene (HTPB) as macrodiol. All the chain extenders were used separately

or in combined form to prepare the different series of polyurethane. By reacting one

equivalent of HTPB with three equivalents of hexamethylene diisocyanate (HMDI), NCO

terminated polyurethane prepolymer (NTP) is formed and then extended with different ratio

of chain extenders curcumin, chitin and BDO to get final PU polymer. Part-1 was prepared

by using the different diisocyanates i.e (HMDI, H12MDI, IPDI, TDI and MDI) with constant

ratio of curcumin/BDO. The synthesized PU polymers were characterized structurally and

morphologically via FTIR, SS1HNMR and SEM techniques respectively. Thermal properties,

crystallinity behaviors, biological activity (antimicrobial and antifungal activity), water

absorption and degree of swelling tests were performed to optimize the various properties of

PUs. The detailed discussion of the obtained results is given under different sections.

Part-I

4.1 Molecular and Biological Characterization of Novel Curcumin Based

Polyurethanes of Varying Diisocyanates

4.1.1 Molecular characterization

FTIR technique was used to study the proposed structures of synthesized PUs, monomers and

chain extenders in the region of 4000-400 cm-1

. In figure 4.1 the FTIR spectra of curcumin,

chitin, BDO, HTPB and HMDI are presented. In (Figure 4.1a) spectrum of hydroxyl

terminated polybutadiene presented the extending vibrations of ═C─H at 3030 cm-1

, the

preoccupation peaks at 955 cm-1

, 922 cm-1

and 690 cm-1

have been correlated with trans,

vinyl and cis structures of HTPB (Vilar et al., 1997). The FTIR spectrum of HTPB shows the

broad OH peak which has been appeared at 3386.24 cm-1

. Whereas, ─CH2 asymmetric and

symmetric stretching is represented at 2924.33 cm-1

and 2838.75 cm-1

, ─C═C stretching has

been appeared at 1509.16 cm-1

. The peak at 3512 cm-1

is due to out of plane twist of OH

group.

In (Figure 4.1b) FTIR spectrum of HMDI presented the peaks at 2934.26 cm-1

,

2826.65 cm-1

due to asymmetric and symmetric elongation of hydrocarbon (─CH2).

Prominent peak at 2252.16 cm-1

is due to NCO group present in HMDI. Due to C─H

72

stretching vibrations the hydrocarbons show IR absorption peaks between 2824 cm-1

and

3340 cm-1

. The peaks 2845 –3010 cm-1

is due to the hybridized sp3 carbon (C─H). The

(Figure 4.1c) represents the BDO spectrum, peak of regular (symmetric) and irregular

(asymmetric) stretching of the ─CH2 groups at 2885.63 cm-1

and 2942.66 cm-1

respectively.

Inter and intramolecular H-bonding and corresponding OH group broad band peak is

appeared at 3342.26 cm-1

. Due to primary alcohol groups a prominent peak appeared at

1056.35 cm-1

(Lin et al., 1991). In figure 4.1d the FTIR spectrum of CUR, in which peak at

3510 cm-1

showed phenolic OH stretching vibrations, the peak at 2937 cm-1

of anti-

symmetrical CH2 stretch, enol-carbonyl stretching vibration showed at 1636 cm-1

. The

hydrocarbon bonds elongation showed the broad absorbance peak area in the range 1610 and

1410 cm-1

(Chereddy et al., 2013). The peak values due to benzene sphere widening

vibration, C═O, C─C shakings, and olefinic hydrocarbon bending trembling are presented at

1595 cm-1

, 1505 cm-1

, and 1434 cm-1

(Yallapua et al., 2010; Wang et al., 2008). The peaks

appeared at 1268 cm-1

, 1188 cm-1

, 1155 cm-1

and 1035 cm-1

due to C─O elongation (Souguir

et al., 2013; Anitha et al.,2011). In figure 4.1e showed the spectrum of chitin, the peak at

3454.26 cm-1

is due to OH stretching vibrations. Peaks showed at 3271cm-1

and 3122 cm-1

is

due to NH symmetric and asymmetrical stretching vibraions. The peaks at 2886.22 cm-1

and

2988.42 cm-1

are because of CH regular (symmetric) and irregular (asymmetric) stretching

vibrations. Peaks region from 685.46-1726.66 cm-1

provides great information. The C═O

bond peak showed at 1726.44 cm-1

. CH2 wagging, CH and CH2 bending vibrations are

showed at 1322.11 cm-1

, 1368.10 cm-1

and 1433.55 cm-1

. The OH and NH bending vibration

peaks are appeared in range of 1248.77 cm-1

and 1211.22 cm-1

. Asymmetric in-plane ring

deformation peak showed at 1166 cm-1

, carbonyl and alkene stretching vibration peaks at

1048 cm-1

and 1033 cm-1

. The C═O loop trembling and circle meandering showed peaks at

948 and 889 cm-1

. The band peaks within 1010-1215 cm-1

are due to ring and bond C─O─C

shakings of chitin-ether-type bonding. The amide group due to out of plane bending showed

weak and well resolved peaks at 715 cm-1

and 679 cm-1

.

73

Figure 4.1: FTIR spectra of monomers: (a) hydroxyl terminated polybutadiene (HTPB)

(b) hexamethylene diisocyanate (HMDI) (c) 1,4-butane diol (BDO) (d) curcumin and (e)

chitin

74

The FTIR spectrum of HMDI shows peaks of anti-symmetric and symmetric stretching, and a

sharp NCO peak in the regions as explained above. The prominent FTIR peaks of IPDI

(2953.02cm-1

─CH2 stretching, and 2247.07cm-1

─NCO group), H12MDI (2929.87cm-1

─CH2

anti symmetric stretching and 2854.55 cm-1

symmetric stretching, and 2249.00cm-1

─NCO

group), TDI (broad peak at 2950 cm-1

─CH2 stretching vibration , sharp peak at 2241.28cm-1

─NCO group linked with toluene diisocyanate and C═C bond at 1580.49 cm-1

), and MDI

(CH2 broad stretching peak at 2883 cm-1

, 2277.93cm-1

─NCO group, and 1512.19 cm-1

of

C═C) are mentioned in figure 4.2 (a-e) respectively.

FTIR spectra of PU extended with the blends of BDO/curcumin with varying

diisocyanate structures (IPU1-IPU5) were studied and discussed. The FTIR spectrum of IPU3

(having isophorone diisocyanate) is shown in figure 4.3. The FTIR spectrum of IPU3 shows

the major peak at 3321 cm-1

due to ─NH and ─OH stretching peaks overlap. Whereas ─CH2

asymmetric and symmetric stretching is represented at 2918 cm-1

and 2846 cm-1

, ─C═O

stretching has been appeared at 1689 cm-1

. The shoulder peak due to enol-carbonyl stretching

is appeared at 1647cm-1

, while the peaks at 1533cm-1

and 1442cm-1

(C─H aromatic ring

stretching), 1255cm-1

(CN stretching), and 1139cm-1

(C─O stretching).

75

Figure 4.2: FTIR spectra of various diisocyanates (a) HMDI (b) IPDI (c) H12MDI (d)

TDI (e) MDI

76

Figure 4.3: FTIR spectrum of polyurethane extended with blends of curcumin and 1,4-

butane diol (IPU3)

77

4.1.2 Scanning electron microscope (SEM) analysis

The SEM technique was employed to investigate the morphology of fractured surface of the

polyurethanes extended with blends of curcumin/1,4-butane diol by using different

diisocyanates. It can be depicted from the images of sample IPU1 (Figure 4.4a at different

resolutions) that no ordered packing is observed due to aliphatic diisocyanate into the back

bone of PU. Furthermore, a continuous phase is visible in SEM micrographs, which is created

by the amorphous part of the soft phase and the intermediate phase, i.e., the so-called matrix.

In the figure 4.4a (at high resolution 25000µm), no projecting crystallization has been

observed in the sample (IPU1). However, the images of the sample IPU5 (Figure 4.4e) have

shown the presence of ordered pattern. In the figure 4.4e, a prominent crystallization can

clearly be observed in curcumin/BDO based PU having methylene diphenyl diisocyanate

structure (IPU5). The results from the SEM images revealed non-packing to packing

arrangements (Figure 4.4 b-d) as observed from IPU2 to IPU4. It is worth to mention that

cross-linked material do not show any crystallization behavior so the observed pattern may be

due to the ordered packing because of aromatic diisocyante into the backbone of

polyurethane. The compatibility of two kinds of polymer could be evaluated from the degrees

of homogeneity and compactness of the blended film. The result of SEM indicates that there

is a change in surface micro-structure and resulting heterogeneous surface upon the reaction

of PU prepolymer with that of curcumin/BDO material.

78

Figure 4.4: SEM images of polyurethanes extended with the blend of curcumin and 1,4-

butane diol

79

4.1.3 Biological activity analysis

4.1.3.1 Antimicrobial and antifungal activity

The antimicrobial activity test including anti-bacterial and anti-fungal test for different

samples of the curcumin based polyurethane was studied in order to determine the

biocompatibility of the prepared PU samples. The antimicrobial activity observed for all the

prepared curcumin based polyurethane samples is presented in table 4.1, whereas the

antifungal activity results are presented in table 4.2. Agar diffusion method was applied in

which disc of the sample was 12mm and slandered size of the disc was taken as 6mm and

concentration of the antibiotic was taken as 25µg/disc against various antibacterial strains

(Staphylococcus aureus, Bacillus subtilis, Pasturella multocida, Escherichia coli). From the

results of the previous studies, it was inferred that by increasing the concentration of the

curcumin, the antibacterial as well as antifungal activity increased (Chen et al., 2014; Sun et

al., 2013). Antimicrobial activity results of this investigation found an increase in anti-

microbial activity as the structure of diisocyanate changed from aliphatic to cycloaliphatic

and then aromatic. The results presented in tables 4.1 & 4.2 depicted that the inhibition zone

of the control sample is less as compared to the curcumin based polyurethanes and the

inhibition zone for all the curcumin based polyurethane is increased (IPU to IPU5) replacing

the aliphatic to aromatic character of diisocyanate.

The antifungal strains: Aspergillus niger, Aspergillus flavus, Ganoderma lucidum,

Alternaria alternata were used to determine the antifungal activity of the curcumin based

polyurethanes (Table 4.2).

Comparison of PU1 to PU5 suggested the better results of PU5 (with aromatic

character) as compared to former. Thus both PU4 and PU5 displayed more pronounced

biocompatible behavior than former. While the other three samples designated as PU1, PU2

and PU3 having aliphatic and cyclo-aliphatic structures, respectively in their formulation

showed some toxic and incompatible behavior. It is worth mentioning that very small amount

of catalyst added to these samples (PU1, PU2 and PU3) owing to least reactivity of aliphatic

isocyanates resulted in toxic behavior. Additionally degradation products (such as aromatic

diamines) of aromatic diisocyanates are also toxic and carcinogenic compounds, thereby

making them undesirable for in vivo applications. Heavy metal organometallic compounds,

such as dibutyl tin dilaurate (DBTDL), stannous octoate, and tertiary amines may be used to

catalyze reactions leading to polyurethanes. Catalysts of either type remain as a leachable

residue in the final product. Since it is known that both types of catalysts, particularly

organometallic materials is highly toxic, and residual tertiary amine leaves an objectionable

80

odor (Rhodes et al., 1994). It is worthwhile mentioning that better properties are achievable

by the use of aromatic diisocyanates. While synthesizing a biomaterial, it is very essential to

consider its properties regarding its end use along with biocompatibility and toxicity.

A small amount of catalyst was used in the samples having aliphatic or cyclo-aliphatic

structure of diisocyanate. The results showed that use of catalyst have adverse effects on the

biocompatibility of the samples. The samples which have been synthesized by the use of

catalyst show toxic behavior as compared to those which have been prepared without the use

of catalyst. These results are in accordance with the results that catalyst with organometallic

character are highly toxic and leaves an objectionable odor as reported earlier (Rhodes et al.,

1994) which make the polymer film non-biocompatible.

Table 4.1: Antibactrial activity of the curcumin based polyurethanes, inhibition zone

(mm)

Sample Code Staphylococcus

aureus

Bacillus

subtilis

Pasturella

multocida

Escherichia

coli

IPU1 13 14 14 14

IPU2 21 22 18 20

IPU3 23 23 21 21

IPU4 25 24 23 22

IPU5 27 28 25 23

Rimpacin 28 27 24 25

81

Table 4.2: Antifungal activity of the curcumin based polyurethanes, inhibition zone

(mm)

Sample Code Aspergillus

niger

Aspergillus

flavus

Ganoderma

lucidum

Alternaria

alternate

IPU 1 13 14 - -

IPU 2 15 215 - 11

IPU 3 17 16 13 15

IPU 4 18 17 14 17

IPU 5 20 18 15 18

Fluconazole 23 24 19 22

82

Part-II

4.2 Molecular, Thermal and Surface Characterization of Chitin /

Curcumin / BDO Blends Based Polyurethanes


Figure 4.5a showed the FTIR spectrum of PU prepolymer where OH peak is not observed

and the intensity of NCO peak has been reduced, which confirms the reaction between NCO

and OH group of polyol. The peak at 3335.33 cm-1

appeared in spectrum is due to NH group

that confirmed the formation of prepolymer. The peaks in polyurethane prepolymer spectrum

such as CH2 asymmetric stretching showed peak at 2924.55 cm-1

; symmetric stretching of

CH2 showed peak at 2852.78 cm-1

; NCO was observed at 2277.33 cm-1

; carbonyl group peak

was observed at 1715.66 cm-1

; and CH2 bending at 1444.13 cm-1

. In figure 4.5b the spectrum

of BDO based polyurethane is presented, which showed peaks; at 3344.18 cm-1

due to NH

group; CH2 asymmetric at 2922.44 cm-1

; CH2 symmetric presented peak at 2844.86 cm-1

;

carbonyl group at 1722.77 cm-1

; NH deformation at 1589.14 cm-1

, 1533.88 cm-1

; and C─O

elongating peak at 1218.66 cm-1

. In figure 4.5c the spectrum of curcumin based polyurethane

represented the peak at 3334.28 cm-1

is due to NH group; CH2 asymmetric stretching peak at

2933.55 cm-1

; CH2 symmetric stretching is at 2855.46 cm-1

; C═O group peak was observed at

1735.65 cm-1

; NH deformation showed peaks at 1579.24 cm-1

, 1537.74 cm-1

; C─O elongating

peak was observed at 1228.36 cm-1

. In figure 4.5d the spectrum of chitin based polyurethane

is presented, spectrum showed the following peaks: peak at 3337.48 cm-1

is due to NH group;

due to CH2 asymmetric peak showed at 2944.65 cm-1

; hydrocarbon symmetric presented peak

at 2852.37 cm-1

; C═O group peak observed at 1725.88 cm-1

; NH deformation showed peaks

at 1576.34 cm-1

, 1542.64 cm-1

; C─O elongating peak was observed at 1222.26 cm-1

. Analysis

of FTIR in figure 4.5b, 4.5c & 4.5d showed that there is no ─NCO peak and the broad peak

of N─H confirmed the completion of reaction. The value of peaks within 3305–3355 cm-1

endorsed the presence of N─H stretching (Williams & Flemming, 2006).

83

Figure 4.5: FTIR spectra of polyurethane prepolymer and final product of polyurethane

to confirm the PU formation: (a) PU prepolymer (b) BDO based polyurethane (c)

curcumin based polyurethane and (d) chitin based polyurethane

84

According to the formulations given in table 3.2, the mixtures of curcumin, chitin and 1,4-

butanediol in various ratios were used for the extension of polyurethane prepolymer. In

reaction scheme 3.2d, the preparation of curcumin/chitin/1,4-butanediol based PU is

elaborated and in figure 4.6 the FTIR spectra are presented. The polyurethane prepolymer

(Figure 4.5a) was extended with mixture of BDO (Figure 4.1c)/curcumin (Figure 4.1d)/chitin

(Figure. 4.1e) with various ratios i.e., 1:0.5:0.5, 0.5:1:0.5 and 0.5:0.5:1 to make polyurethane

sheets. The FTIR spectrum of 1,4-butanediol/curcumin/chitin (1:0.5:0.5) based polyurethane

is shown in figure 4.6b. The FTIR spectrum of 1,4-butanediol/curcumin/chitin (0.5:1:0.5)

centered polyurethane is given in figure 4.6c. The FTIR spectrum of 1,4-

butanediol/curcumin/chitin (0.5:0.5:1) based polyurethane is given in figure 4.6d. In figure

4.6b the KPU4 spectrum elaborate the prominent peaks at 3338.15 cm-1

(NH groups);

2935.24 cm-1

and 2838.76 cm-1

(CH2 asymmetric and symmetric stretching); 1715.27 cm-1

(carbonyl group); 1628.17 cm-1

(enol-carbonyl elongation) ; 1579.23 cm

-1, 1521.66 cm

-1 (NH

deformation ) ; 1215.37 cm

-1 (C─O broadening observed ); 1148.88 cm-1

(C─O─C). In figure

4.6c the major peaks in KPU5 spectrum is also lied in the same region with wave numbers

3324.88 cm-1

(NH) ; 2923.65 cm-1

(CH2 asymmetric); presented peak at 2846.36 cm-1

(CH2

symmetric); 1725.44 cm-1

(C═O); 1624.88 cm-1

(enol-carbonyl); 1574.17 cm-1

, 1524.55 cm-1

;

(NH deformation); 1218.22 cm-1

(C─O broadening observed); 1145.66 cm-1

(C─O─C). In

figure 4.6d the spectrum of KPU6 presented peaks at: 3342.52 cm-1

; 2942.44 cm-1

; 2839.46

cm-1

; 1723.88 cm-1

; 1621.55 cm-1

1576.77 cm-1

, 1542.99 cm-1

; 1223.44 cm-1

. Analysis of

FTIR in figures 4.6b, 4.6c & 4.6d showed that there is no ─NCO peak and the presence of

wide peak of N─H confirmed the completion of reaction. Peaks between the values of 3305–

3355 cm-1

endorsed the occurrence of N─H stretching (Williams & Flemming, 2006).

85

Figure 4.6: FTIR spectra of polyurethane prepolymer and final product of polyurethane

to endorse the planned PU structure: (a) PU prepolymer (b) BDO (50%) / curcumin

(25%) / chitin (25%) based polyurethane (c) BDO (25%) / curcumin (50%) / chitin

(25%) based polyurethane and (d) BDO (25%) / curcumin (25%) / chitin (50%) based

polyurethane

86

4.2.2 Solid state proton nuclear magnetic resonance spectroscopic (SS1HNMR) analysis

The quest for understanding the relationship between physical properties and molecular

motions in solid polymers has piqued the interest of scientists since the formation of polymer

science (Flory, 1953; Volkenstein, 1963). Despite the multiple attempts by physical chemists

to understand the molecular origins of solid-state polymer properties, all quantitative theories

have been limited to describe the general and ideal behavior. With the advent of methods

such as neutron scattering and solid state nuclear magnetic resonance (NMR) enabled the

scientists to directly probe the molecular characteristics of polymers in the solid state. 1H

solid state NMR spectra of 100% BDO (KPU1), 100% curcumin (KPU2), 100% chitin

(KPU3) and blends of 25/25/50 % of BDO/curcumin/chitin respectively (KPU6) are shown in

figures 4.7, 4.8, 4.9 & 4.10. In all the spectra of KPU1, KPU2, KPU3 and KPU6 the chemical

shift value of protons attached to sp3 hybridized carbon lies in the range of 0-4.5 ppm. The

values of NH group, ═C─H group, and aromatic ring attached protons lies in the range of

4.5-8.5 ppm. SS1HNMR spectrum in figure 4.7: 8.40 ppm (H8); 7.4 ppm (H7); 4.4 ppm

(H5,H6); 3.48 ppm (H4); 3.20 ppm (H3); 2.43 ppm (H2); 1.54 ppm (H1). Figure 4.8

spectrum: 8.49 ppm (H13); 7.6-7.4 ppm (H7-H12); 4.47 ppm (H4, H6); 3.7 ppm (H5); 3.24

ppm (H3); 2.46 ppm (H2); 1.56 ppm (H1). Figure 4.9 spectrum: 8.43 ppm (H15); 7.42 ppm

(H14); 4.48 ppm (H8,H10,H13); 4.41, 4.35, 2.45, 4.12, 3.78, 2.05, 2.40 ppm (H4, H5, H6,

H7, H9, H11, H12); 3.21 ppm (H3); 2.42 ppm (H2); 1.52 ppm (H1). Figure 4.10 spectrum:

8.45 ppm (H24); 7.35-7.44 ppm (H18-H23); 2.10, 4.38, 3.68, 4.44, 2.47, 4.29, 4.10, 4.42,

2.43, 4.44, 3.75, 4.43, 3.46, 4.41 ppm (H17, H16, H15, H14, H13, H12, H11, H10, H9, H8,

H7, H6, H5, H4) respectively. 3.23 ppm (H3); 2.44 ppm (H2); 1.55 ppm (H1).

87

Figure 4.7: Solid state 1H NMR spectrum of BDO based PU (KPU1)

88

Figure 4.8: Solid state 1H NMR spectrum of curcumin based PU (KPU2)

89

Figure 4.9: Solid state 1H NMR spectrum of chitin based PU (KPU3)

90

Figure 4.10: Solid state 1H NMR spectrum of curcumin/chitin/BDO blends based

PU (KPU6)

91

4.2.3 Scanning electron microscopy (SEM) analysis

SEM is an analytical technique which is employed to study the surface morphology of

prepared polyurethane samples. It provides the images of observed surfaces by interaction

with an intense ray of electrons. Upon interaction of electrons with the atom of the sample

under investigation, the signals are produced which give an insight about the surface

morphology. This information is helpful to understand the compatibility of two different

kinds of polymers and composition through topographical images. The surface morphology

of synthesized polyurethane samples (KPU1-KPU6) were studied by using SEM and

resulting images are presented in figure 4.11. These images give the information about the

incorporation of chitin/curcumin/BDO in prepared PU samples. By increasing the

concentration of chitin the stability increased and cracking decreased. In SEM image of

KPU3 (Figure 4.11) it is clearly shown that there might be physical crosslinking that

generated ordered pattern (crystallization region can be observed). While in SEM images

KPU1 and KPU2 (Figure 4.11) such behavior is missing. The SEM images of blends

(chitin/curcumin/BDO) based PU samples KPU4, KPU5 and KPU6 (Figure 4.11) showed

that by increasing the mole ratio of chitin the ordered pattern and crystallization regions

become more prominent and this is not observed in the PU samples with decreasing

proportions of chitin. From these results the participation of chitin material into the

polyurethane prepolymer has been confirmed which has the ability to form network structure.

The results show that surface microstructure has been changed and the subsequent dissimilar

surface is due to final interaction between polyurethane prepolymer with that of

chitin/curcumin/BDO.

92

Figure 4.11: SEM images of pristine and blends of chitin, curcumin and BDO based

PUs, KPU1-KPU6

93

4.2.4 X-Ray Diffraction Analysis

X-ray diffraction analysis was carried out in order to find out the changes in the crystalline

structure upon the substitution reaction with NCO-terminated prepolymer. In segmented PUs,

phase separation of soft segments (SS) and hard segment (HS) can take place depending on

their relative contents, structural regularity and thermodynamic incompatibility. The X-ray

diffraction studies showed that crystallinity is much dependent on the structure of

diisocyanates and chain extender in the polyurethane backbone. The high crstallinity is

reported in chitin (Zia et al., 2008; Zia et al., 2009) which increases as the concentration of

chitin in to the final PU is increased. The characteristic peaks of curcumin can be attributed to

the traits of a high crystalline structure (Liu et al., 2016). X-ray diffraction showed the

crystallinity of Cur-CH film was lower than pure chitosan film (Liu et al., 2016). Zia et al. in

2008 reported that the crystallinity decreased from aliphatic to aromatic characters of the

diisocyanates used in the final PU. The reported literature showed that the well oriented

crystallinity are observed at about 2θ = 20°-22

°. Figure 4.12 presented X-ray diffractograms

of pristine and blends of chitin, curcumin and BDO based PUs, KPU1-KPU6. The X-ray

diffraction studies confirmed the previous results that crystallinity increased as the

concentration of chitin in to the final PU increased (Figure 4.12). All samples showed

crystalline behavior due to aliphatic diisocyanate structure, but intensity of peaks at different

2θ values were observed due to different chain extenders. The 2θ values of crystalline peaks

of KPU3, KPU6, KPU5, KPU4, KPU2 and KPU1 are 21°, 18.5

°, 16.8

°, 15.8

°, 17.5° and 15.5

°

respectively. Although curcumin possesses crystalline behavior according to reported

literature but an opposite behavior in curcumin and chitin loaded elastomer was possibly due

to formation of an amorphous complex with the intermolecular interaction occurring within

chitin and curcumin molecules, which decreases the crystallinity. On the other hand chitin; a

crystalline polymer of N-acetyl-D glucosamine monomers, is capable of forming three

dimensional ordered structures, because of the ability of the acetamide group to form

hydrogen bonds. The PU extended with 100% chitin KPU3 and with combination of

chitin/curcumin/1,4-BDO showed the higher peak intensities leading us to conclude that these

samples present the higher chain orientation degree. These results confirmed that the

crystalline patterns vary with the type of chain extender.

94

Figure 4.12: X-ray diffractograms of pristine and blends of chitin, curcumin and BDO

based PUs, KPU1-KPU6

95

4.2.5 Thermal characteristics

4.2.5.1 Thermogravimetric (TGA) analysis

Thermogravimetric (TGA) analysis is a very helpful technique to examine the decomposition

process of PUs (Javni et al., 2000). Figure 4.13 showed the TG curves of pristine BDO,

curcumin, chitin based PU (KPU1-KPU3) and blends of BDO/curcumin/chitin based

polyurethanes (KPU4-KPU6). The TGA curves showed that the weight loss occurred in two

prominent stages. In first stage at temperature 200 to 300 °C there was a small change in

weight occurred due to loss of moisture. While in the second stage weight loss was observed

at the temperature range of 300-500 °C due to thermal degradation of polymers. In the first

stage the weight loss rates are nearly equal, but in second stage there is difference in

degradation temperature. A high decomposition temperature was observed for KPU3 than

KPU1 and KPU2. N-acetyl-D-glucosamine is the basic unit of chitin that enhanced the

thermal resistivity of chitin molecule as compared to 1,4-butanediol and curcumin molecules

(Moussian et al., 2005). The keto-enol structure of curcumin made it possible to create more

stable PU and enhance its intractability with polyurethane, therefore thermal stability of

curcumin based PU is better than BDO based PU. Chen et al. (2014) reported that curcumin

is decomposed in two steps, in first step the substituent group of curcumin is decomposed and

after this decomposition of benzene rings are started. In this work an increase in final

decomposition temperature of pristine chitin based PU is observed owing to effective

interaction stability between chitin and polyurethane prepolymer. The decomposition

temperature of KPU3 is greater than KPU1 and KPU2 due to crosslinking behavior of chitin

molecule. However, the samples KPU4, KPU5, KPU6 showed a relative decreasing trend in

decomposition temperature as the concentration of chitin decreased. The samples in which

large amount of chitin was used in the form of blend showed more crosslinking behavior as

compared to the samples with lower quantity of chitin used. The temperature value at which

20% weight loss occurred of KPU1, KPU2, KPU3, KPU4, KPU5 and KPU6 are 325 ºC, 360

ºC, 400

ºC, 365

ºC, 375

ºC and 385

ºC respectively. The results of comparative study regarding

the thermal behavior of KPU1, KPU2, KPU3, KPU4, KPU5 and KPU6 showed that the

samples with higher concentration of chitin are thermally stable. Thermogravimetric analysis

(TGA) of PU blends indicated a better thermal stability with 1 M:0.5 M:0.5M of chitin,

curcumin and BDO respectively . From this it has been inferred that the blends with high

concentration of chitin showed high thermal stability as compared to curcumin/BDO. Hence,

chitin possesses a crystalline character which has N-acetyl-D-glucosamine monomers, at

96

higher temperature chitin degraded but not melted (Chen et al., 2004). Secondly, in blend

form chitin increases the stability and thermal characters of synthesis material. Lundberg and

Cox (1969) have reported that the PU with large crosslinking show better thermal strength.

Figure 4.13: TGA curves of polyurethane samples (KPU1-KPU6)

97

4.2.5.2 Differential scanning calorimetery (DSC)

Figure 4.14 represents the DSC curves of pristine BDO, curcumin, chitin based PU

respectively (KPU1-KPU3) and blends of BDO/curcumin/chitin based PU (KPU4-KPU5).

From DSC thermograms we evaluate the glass transition temperature (Tg), crystallization

temperature (Tc), melting temperature (Tm) and decomposition temperature (Td) of

synthesized polymer samples. The glass transition temperature (Tg) is the temperature below

which polymer behaves like hard glass while above this temperature it behaves like rubbery

or soft form. The chemistry of polymer, degree of crosslinking, degree of crystallization and

size of branching groups effect on Tg value. Generally, in DSC curves the higher temperature

point is due to Tc. At Tc point by heating the material the next temperature will be melting

temperature (Tm). During melting stage sample absorbs heat, and show endotherm peak. In

this project, DSC technique was implied to examine the crystallinity and heat fluctuation of

synthesized chitin/curcumin/BDO based PU samples by using an instrument SDT Q 600

V20.9 Build 20. After weighted amount of the samples were studied in temperature range

from 25 ºC to 625

ºC at the rate of 10

°C/min under N2 atmosphere. The effect of chain

extenders; chitin, curcumin and BDO in the backbone of HTPB/HMDI centered polyurethane

material were examined by DSC analysis. By increasing the temperature from 25 °C-625

°C,

evident changes were observed in all polyurethane samples. From DSC thermograms it was

observed that KPU1-KPU6 showed Tg, Tc and Tm peaks. From the figure 4.14 it has been

observed that thermal stability and crystallinity are being decreased by decreasing the

quantity of chitin and curcumin as compared to BDO. Curve of sample KPU3 showed more

crystallinity and thermal stability as compared to other samples of polyurethanes. The

chemical crosslinking behavior also plays its role for such thermally stable PU. Chitin formed

a crosslinking with the backbone of PU, which enhance its crystallinity and stability as

compared to curcumin and BDO based PU. While the stable keto-enol structure of curcumin

along with intermolecular hydrogen bonding with PU make it more stable than BDO based

PU. The DSC curves of KPU4, KPU5 and KPU6 showed that in blended PU samples, the

crystallinity and thermal stability are being increased by increasing the mole ratio of chitin.

98

Figure 4.14: Differential scanning calorimetery (DSC) curves of samples KPU1-KPU6

99


4.2.6.1 Assessment of water absorption and equilibrium degree of swelling

The physical behavior of prepared polyurethane materials such as water absorption and

degree of swelling were calculated and enlisted in table 4.3 and table 4.4 separately. The

synthesized curcumin/chitin/BDO based polyurethane samples were dipped in water for

seven days. The data was collected on daily basis and it is presented in table 4.3. From the

observations it was cleared that the amount of water absorption depends on the chain

extenders i.e., BDO, curcumin and chitin. The results of table 4.3 showed that the synthesized

samples with higher concentration of chitin showed better hydrophobic behavior as compared

to the sample with lower concentration of chitin. When we compared the effect of pristine

chitin based PU and chitin-curcumin blended, the result showed that chitin based PU has

lower water absorption character as compared to chitin-curcumin blended. In the blended

form curcumin enhances the interaction of chitin with PU backbone, therefore the absorption

properties of blends based PU has been increased. The stable keto-enol structure of curcumin


PU, therefore water absorption character of curcumin based PU is lower as compared to BDO

based PU. The swelling behavior results of prepared polyurethane samples are given in table

4.4. From the data it is evident that the swelling character of polyurethane elastomers has

been decreased by increasing the quantity of chitin as compared to curcumin and BDO in PU

samples. In contrast to the stable keto-enol structure of curcumin along with intermolecular

hydrogen bonding with PU reduces the swelling capability of polyurethane as compared to

BDO based PU. The aqueous immersion and swelling actions of chitin based polyurethane

has been reduced due to chemical crosslinking behavior of multi-functional chitin molecule.

From the above discussion it was inferred that chitin/curcumin/BDO blended PU depict a

unique pattern of physical behavior applicable in biomedical applications as compared to

pristine chitin, curcumin and BDO based PU. We propose it as an appropriate biofunctional

material.

100

Table 4.3: Water absorption of chitin/curcumin/BDO based polyurethane samples

Water absorption (%)a

Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU1 1.110 ± 0.04 1.164 ± 0.06 1.173 ± 0.04 1.179 ± 0.07 1.195 ± 0.07 1.200 ± 0.06 1.213 ± 0.02 1.226 ± 0.06

KPU2 1.140 ± 0.03 1.186 ± 0.04 1.194 ± 0.06 1.200 ± 0.07 1.217 ± 0.05 1.220 ± 0.07 1.224 ± 0.03 1.237 ± 0.04

KPU3 1.160 ± 0.05 1.171 ± 0.03 1.178 ± 0.03 1.183 ± 0.04 1.187 ± 0.04 1.190 ± 0.05 1.191 ± 0.05 1.191 ± 0.03

KPU4 1.100 ± 0.05 1.134 ± 0.05 1.146 ± 0.02 1.153 ± 0.03 1.157 ± 0.06 1.165 ± 0.05 1.168 ± 0.06 1.174 ± 0.05

KPU5 1.080 ± 0.04 1.110 ± 0.05 1.119 ± 0.07 1.125 ± 0.03 1.129 ± 0.04 1.132 ± 0.06 1.134 ± 0.07 1.139 ± 0.06

KPU6 1.090 ± 0.01 1.118 ± 0.02 1.124 ± 0.03 1.129 ± 0.05 1.134 ± 0.06 1.138 ± 0.07 1.140 ± 0.03 1.140 ± 0.08

* Sample weight of untreated sample

a Each value of water absorption (%) is expressed as mean ± standard error (S.E) (n=3)

101

Table 4.4: Swelling actions of chitin/curcumin/BDO based polyurethane samples

Sample

number

Sample

code

Density

(g/cc)

Swelling behavior of PU samples Equilibrium

degree of

swelling

(1/vR)a

0 day*

1st day 3

rd day 5

th day 7

th day

1 KPU1 1.024 1.20 1.67 1.94 2.06 2.03 1.99 ± 0.08

2 KPU2 1.033 1.19 1.63 1.73 1.78 1.76 1.86 ± 0.10

3 KPU3 1.053 1.15 1.54 1.59 1.57 1.55 1.49 ± 0.00

4 KPU4 1.047 1.11 1.51 1.59 1.62 1.60 1.62 ± 0.11

5 KPU5 1.049 1.18 1.60 1.67 1.68 1.66 1.55 ± 0.16

6 KPU6 1.051 1.21 1.63 1.69 1.68 1.67 1.51 ± 0.10

*Sample weight of untreated sample

a Each value is expressed as mean ± standard error (S.E) (n=4)

102

Part-III

4.3 Molecular, Thermal and Surface Characterization of Curcumin / BDO

Blends Based Polyurethanes


Figure 4.15 (a, b, c and d) represented the FTIR spectrum of PU prepolymer (a); BDO (75%)

/ curcumin (25%) based polyurethane (b); BDO (50%) / curcumin (50%) based polyurethane

(c) BDO (25%) /curcumin (75%) based polyurethane (d). The comparison of PU prepolymer

and PU blends showed the disappearance of ─NCO peak in the later one and appearance of

N─H peak confirmed the end of reaction. The other prominent peaks are discussed in section

4.2.1. In figure 4.15b the main peaks are observed at the following range of wave numbers

i.e., 3333.22 cm-1

(─NH ); 2933.22 cm-1

and 2822.66 cm-1

( respective asymmetric and

symmetric CH2 stretch) , 1711.55 cm-1

(C═O); 1577.22 cm-1

, 1544.66 cm-1

(─NH

deformation); and 1222.77 cm-1

(C─O). Figure 4.15c, showed peaks at 3322.66 cm-1

(─NH);

2944.33 cm-1

(CH2 asymmetric), 2866.33 cm-1

(CH2 symmetric); 1747.44 cm-1

(C═O);

1568.33 cm-1

, and 1546.65 cm-1

(─NH deformation); 1233.25 cm-1

. In Figure 4.15d the

notable peaks are 3329.55 cm-1

(─NH), 2936.54 cm-1

(CH2 asymmetrical), 2860.22 cm-1

(CH2 symmetrical), 1733.66 cm-1

(C═O); 1558.55 cm-1

, 1566.33 cm-1

(─NH deformation),

and 1219.17 cm-1

(C─O).

103

Figure 4.15: FTIR spectra of PU prepolymer and final PU to confirm the proposed

polyurethane structure: (a) PU prepolymer, (b) BDO (75%) / curcumin (25%) based

polyurethane, (c) BDO (50%) / curcumin (50%) based polyurethane and (d) BDO

(25%) / curcumin (75%) based polyurethane

104

4.3.2 Solid state proton nuclear magnetic resonance spectroscopy (SS1HNMR) analysis

The solid state 1H NMR spectrum of BDO/curcumin (KPU8) is shown in figure 4.16 presents

the chemical shift value of protons attached to sp3 hybridized carbon in the range of 0-4.5

ppm. The values of protons attached to ─NH group, and ═C─H group, and aromatic ring are

depicted in the range of 4.5-8.5 ppm. SS1HNMR spectrum of KPU8 showed: 8.41 ppm

(H15); 7.38-7.48 ppm (H9-H14); 4.47 ppm (H8); 3.64 ppm (H7); 4.35 ppm (H6); 4.39 ppm

(H5); 3.43 ppm (H4); 3.25 ppm (H3); 2.39 ppm (H2); 1.54 ppm (H1).

Figure 4.16: Solid state 1H NMR spectrum of BDO/curcumin blends based PU (KPU8)

105


The surface morphology of the synthesized polyurethane samples (KPU1, KPU2) and

(KPU7-KPU9) were analysed and compared by using SEM in figure 4.17. It is observed that

by increasing the concentration of curcumin the stability of samples increased and cracking

decreased. In SEM image of KPU2 (Figure 4.17), a smooth and ordered pattern were

observed, no showed appreciable change in morphology. While in SEM image of KPU1

(Figure 4.17) was not observed of such behavior. The SEM images of blended

(curcumin/BDO) PU samples KPU7, KPU8 and KPU9 (Figure 4.17) showed that by

increasing the mole ratio of curcumin the ordered pattern and smoothness of regions become

more prominent, which is not observed in PU samples with decreasing proportion of

curcumin. From these results the participation of curcumin material into the polyurethane

prepolymer has been confirmed which has the ability to retain stable morphology. The

observations show that the surface microstructure has been changed and the subsequent

dissimilar surface is due to the final interaction between polyurethane prepolymer with that of

curcumin/BDO.

106

Figure 4.17: SEM images of pristine and blend of curcumin and 1,4-butane diol based

polyurethanes (KPU1,KPU2) and (KPU7-KPU9)

107

4.3.4 X-Ray Diffraction Studies

To understand the crystal structure of pristine curcumin, BDO based PUs and blends of

curcumin/BDO based PUs were studied using X-ray diffraction patterns between 5 and 45 of

2θ in figure 4.18. The separation of two phases in polyurethanes is due to difference in

structure and properties of incorporated materials. The used technique confirmed that the

diisocyanates and chain extenders play a key role in crystallinity. Kovacevic et al. (1990 &

1993) reported the crystallinity of PU elastomers is due to the soft segments. It is also

reported in the literature, when the hard segments are annealed or present at higher

concentration, present diffraction peak at about 2θ = 11.12° approximately. The HTPB used

in this study has cis (C), trans (T) and vinyl (V) based contributing structures. The ratio of the

contributing structures is trans 52.3% vinyl 33.4% and cis 14.3%. The physical properties of

the polymers are based on the relative isomers. The C═C in the chain induces rigidity and

restrict the conformational freedom for the alignment of segment. Hence, in these polymers

the crystallinity is mainly due to the ordered packing of the hard segments while the HTPB

soft segment restricts the crystalline packing. Hence, the overall behavior of the polyurethane

based on HTPB is amorphous and glassy, resulting in the reduction of the mechanical

strength (Wingborg, 2002). Figure 4.18 showed X-ray diffractograms of pristine and blends

of curcumin and BDO based PUs, (KPU1, KPU2) and (KPU7-KPU9). The X-ray diffraction

studies cleared that crystallinity was depends on the concentration of chain extenders in the

polyurethane backbone, and improved by increasing the mole ratio of curcumin in the final

PU (Figure 4.18). All samples showed crystallinity behavior due to aliphatic diisocyanate

structure, the intensities of peak at different 2θ values vary which is probably because of

different chain extenders. The 2θ values of crystalline peaks of KPU2, KPU7, KPU8, KPU9

and KPU1 are 17.5°, 16

°, 16.4

°, 17.2

°, 15.5

° respectively. These results suggested that the

presence of curcumin as chain extender increased the phase separation as compared to BDO

and the soft segment mobility. The increase in mobility may be responsible for the increase in

the chain alignment grading.

108

Figure 4.18: X-ray diffractograms of pristine and blends of curcumin and BDO based

PUs, (KPU1, KPU2) and (KPU7-KPU9)

109



Figure 4.19 showed the TGA curves of pristine BDO and curcumin based PU (KPU1, KPU2)

and blends of BDO/curcumin based polyurethanes (KPU7-KPU9) respectively. Weight loss

in TG curves occurred in two prominent stages between 200 to 300 °C (loss of moisture) and

300-500 °C (thermal degradation of polymers). A higher decomposition temperature was

observed for KPU2 than KPU1.

The decomposition temperature of KPU2 is higher than KPU1 due to stability of

synthesized material. However, the samples KPU7, KPU8, KPU9 show a relative decreasing

trend in decomposition temperature as the concentration of curcumin decreased. The

temperature value at which 20% weight loss occurred of KPU1, KPU2, KPU7, KPU8, KPU9

are 325 ºC, 360

ºC, 335

ºC, 342

ºC, 350

ºC respectively. The data of comparative study

regarding the thermal behavior of KPU7, KPU8 and KPU9 showed that the samples of

polyurethanes with greater concentration of curcumin as compared to BDO showed greater

thermal stability. Better thermal stability is exhibited by the samples with 1.5 M:0.5 M of

curcumin and BDO respectively. On the whole KPU9 has greater thermal strength as

compared to KPU8, and KPU8 has more thermal stability as compared to KPU7 due to the

difference in the mole ratio of curcumin in mentioned samples.

110

Figure 4.19: TGA curves of polyurethane samples (KPU1, KPU2) and (KPU7-KPU8)

111


Figure 4.20 displays the DSC curves of pristine BDO, curcumin based PU respectively

(KPU1, KPU2) and blends of BDO/curcumin based PU (KPU7-KPU9) under already

prescribed specifications and conditions. The effect of chain extenders curcumin and BDO in

the (backbone of HTPB/HMDI) polyurethane material was examined by DSC analysis. The

distinct thermal and crystalline changes of PU samples were studied (temperature range from

25-625 °C). From DSC thermograms it was observed that KPU1, KPU2 and KPU7-KPU9

showed glass transition temperature (Tg), crystalline temperature (Tc) and melting

temperature (Tm) peaks. Thermal stability and crystallinity have been decreased by

decreasing the quantity of curcumin as compared to BDO (Figure 4.20). The better stability

has been observed for KPU2 as compared to other synthesized samples of polyurethanes. The

chemical interactions of chain extenders with PU backbone played a vital role for the

improvement of thermal stability of PU samples. The stable keto-enol structure of curcumin


PU. The DSC curves of KPU7, KPU8 and KPU9 showed that in blended PU samples, the Tc,

Tm, Tg and thermal stability have been increased by increasing the mole ratio of curcumin.

112

Figure 4.20: DSC curves of polyurethane samples (KPU1, KPU2) and (KPU7-KPU9)

113



The physical characteristics of prepared polyurethane materials such as H2O absorption and

level of swelling were calculated for seven days and have been enlisted in table 4.5 and table

4.6. From the results it was cleared that the amount of water absorption does not depend on

the duration of the time but on the chain extender (curcumin and BDO). The results of table

4.5 showed that the synthesized samples with more curcumin presented more hydrophobic

behavior as compared to the samples with less curcumin. In the blended form BDO enhance

the interaction of PU with water, therefore the absorption properties of the blended PU has

been increased. The stable keto-enol structure of curcumin along with intermolecular

hydrogen bonding with PU make it more stable than BDO based PU. Therefore water

absorption and swelling character (Table 4.6) of curcumin based PU is lower than BDO

based PU. The aqueous immersion and swelling actions of curcumin based polyurethane has

been reduced due to aromatic behavior of curcumin as compared to BDO molecule. Finally, it

may be concluded that curcumin/BDO blended polyurethane possessed multi physical

properties as compared to pristine curcumin and BDO based PU and can be suggested as

good biofunctional material.

Table 4.5: Water absorption of BDO/curcumin based polyurethane samples


Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU1 1.120 ± 0.06 1.175 ± 0.02 1.183 ± 0.06 1.201 ± 0.07 1.206 ± 0.04 1.231 ± 0.05 1.234 ± 0.03 1.236 ± 0.04

KPU2 1.150 ± 0.04 1.185 ± 0.03 1.193 ± 0.07 1.205 ± 0.04 1.210 ± 0.06 1.215 ± 0.05 1.222 ± 0.03 1.222 ± 0.02

KPU7 1.110 ± 0.07 1.155 ± 0.06 1.174 ± 0.02 1.180 ± 0.07 1.195 ± 0.03 1.199 ± 0.06 1.212 ± 0.04 1.214 ± 0.05

KPU8 1.090 ± 0.05 1.134 ± 0.04 1.141 ± 0.06 1.157 ± 0.02 1.162 ± 0.08 1.176 ± 0.04 1.177 ± 0.05 1.178 ± 0.04

KPU9 1.100 ± 0.06 1.138 ± 0.05 1.145 ± 0.07 1.156 ± 0.04 1.161 ± 0.02 1.175 ± 0.04 1.176 ± 0.05 1.176 ± 0.07



114

Table 4.6: Swelling behavior of BDO/curcumin based PU samples

Sample

number

Sample

code

Density

(g/cc)


degree of

swelling

(1/vR)a

0 day*

1st day 3

rd day 5

th day 7

th day

1 KPU1 1.024 1.21 1.68 1.95 2.07 2.04 2.00 ± 0.09

2 KPU2 1.033 1.20 1.64 1.66 1.69 1.68 1.87 ± 0.10

3 KPU7 1.026 1.12 1.52 1.60 1.63 1.63 1.92 ± 0.08

4 KPU8 1.028 1.19 1.61 1.68 1.71 1.69 1.90 ± 0.11

5 KPU9 1.031 1.20 1.63 1.68 1.68 1.69 1.88 ± 0.13



115

Part-IV

4.4 Molecular, Thermal and Surface Characterization of Curcumin /

Chitin Blends Based Polyurethanes


Figure 4.21a showed the major peaks in FTIR spectrum of PU prepolymer (as discussed in

detail under section 4.2.1) and curcumin/chitin-PU (Figure 4.21 b, c, d). In figure 4.21b

(curcumin (75%) / chitin (25%) based polyurethane) presented following peaks at 3338.55

cm-1

(NH group); 2935.55 cm-1

(asymmetric CH2 stretch); 2837.66 cm-1

(symmetric CH2

stretch); 1733.55 cm-1

(C─O, carbonyl group); 1577.33 cm

-1, and 1544.77 cm

-1 (─NH

deformation); C─O 1222.55 cm-1

(C─O elongation). In figure 4.21c (curcumin (50%) /chitin

(50%) based polyurethane), 3322.55 cm-1

(NH stretch); 2922.44 cm-1

and 2866.22 cm-1

(asymmetric and symmetric CH2 stretch); 1740.33 cm-1

(C═O); 1588.19 cm-1

, 1540.66 cm-1

(N─H deformation); and 1233.25 cm-1

(C─O). In figure 4.21d (curcumin (25%) / chitin

(75%) based polyurethane) peaks are at 3344.37 cm-1

2922.69 cm-1

; 2860.24 cm-1

; 1731.77

cm-1

; 1568.25 cm-1

and 1550.56 cm-1

; 1219.17 cm-1

presented N─H stretch, asymmetrical

CH2 stretch, symmetrical CH2 stretch, N─H deformation and C─O elongation. Figure 4.21b,

4.21c & 4.21d showed that there is no ─NCO peak and the broad peak of N─H confirmed the

completion of reaction.

116


polyurethane structure: (a) PU prepolymer, (b) curcumin (75%) / chitin (25%) based

polyurethane, (c) curcumin (50%) / chitin (50%) based polyurethane and (d) curcumin

(25%) / chitin (75%) based polyurethane

117

4.4.2 Solid state proton nuclear magnetic resonance spectroscopy (SS1HNMR) studies

Solid state 1H NMR spectrum of curcumin/chitin (KPU11) represents (Figure 4.22) chemical

shift value of protons attached to sp3 hybridized carbon between 0-4.5 ppm. The values of

NH group, ═C─H group, and aromatic ring attached protons exists in the range of 4.5-8.5

ppm i.e., 8.43 ppm (H22); 7.32-7.47 ppm (H16-H21); 3.62 ppm (H15); 4.44 ppm (H14); 4.38

ppm (H13); 2.13 ppm (H12); 2.45 ppm (H11); 4.42 ppm (H10); 4.13 ppm (H9); 3.77 ppm

(H8); 4.39 ppm (H7); 2.49 ppm (H6); 4.27 ppm (H5); 4.33 ppm (H4); 3.27 ppm (H3); 2.48

ppm (H2); 1.57 ppm (H1).

Figure 4.22: Solid state 1H NMR spectrum of curcumin/chitin blends based PU (KPU11)

118


The surface morphology of synthesized polyurethane samples (KPU2, KPU3) and (KPU10-

KPU12) were studied by using SEM and resulting images have been presented in figure 4.23.

These images give the information about the incorporation of chitin/curcumin in prepared PU

samples. By increasing the concentration of chitin the stability increased and cracking

decreased. The SEM image of KPU3 (Figure 4.23) clearly showed that there might be

physical crosslinking which has generated ordered pattern (crystallization region can be

observed). While in SEM image of KPU2 (Figure 4.23) such behavior is lacked. The SEM

images of blended (chitin/curcumin) based PU samples KPU10, KPU11 and KPU12 (Figure

4.23) showed that by increasing the mole ratio of chitin the ordered pattern and crystallization

regions become more prominent and this is not observed in the PU samples with decreasing

proportions of chitin. From these results, the participation of chitin material into the

polyurethane prepolymer has been confirmed which has the ability to form network structure.

The results show that surface microstructure has been changed and the subsequent dissimilar

surface is due to final interaction between polyurethane prepolymer with that of

chitin/curcumin.

119

Figure 4.23: SEM images of pristine and blends of chitin and curcumin based

polyurethanes, (KPU2, KPU3) and (KPU10-KPU12).

120

4.4.4 X-Ray Diffraction analysis

The crystallinity of the PU samples was estimated by using the intensity of the crystalline

peaks of the respective samples. The d-spacing of different samples was determined by

Debye-Scherer (powder) method using Bragg‟s relation (Castellan, 1996; Han et al., 2005).

Zia et al. (2009) reported that the presence of chitin favor the formation of more ordered

structure. The increase in chitin contents results increasing the intensity of the peak localized

at 2θ = 21.5° confirming that soft segment tend to crystallize generating better defined peak.

X-ray diffraction showed the crystallinity of CUR-CH film was lower than pure chitosan film

(Liu et al., 2016). It suggests that curcumin change the crystallinity in blended form which

indicates the completion of reaction. Zia et al. (2008) described that aliphatic diisocynates

enhanced the crystallinity behavior as compared to aromatic diisocyanats substances. The

reported literature stated the well oriented crystallinity at about 2θ = 20º. Figure 4.24

presented X-ray diffractograms of pristine and blends of curcumin and chitin based PUs

(KPU2, KPU3) and (KPU10-KPU12). From the present study it is clear that crystallinity

improved by increasing the mole ratio of chitin in final PUs as compared to curcumin (Figure

4.24). The 2θ values of crystalline peaks of KPU3, KPU12, KPU11, KPU10, and KPU2 are

21°, 20.2

°, 18.6

°, 17.7

°, 17.5

° respectively. In curcumin molecule, the intramolecular hydrogen

bonding was the primary interaction, consisting of two hydroxyl groups (─OH) in the

benzene ring and the hydroxyl near keto group (C═O) which lowers its intractability as

compared to chitin. On the other hand the chitin which is a crystalline polymer of N-acetyl-D

glucosamine monomers is capable of forming three dimensional ordered structures, because

of the ability of the acetamide group to form hydrogen bonding. By incorporating the

curcumin in chitin based PU the crystallinity change due to the formation of amorphous

region. It is observed that PU extended with 100% chitin (KPU3) and blended samples of

chitin/curcumin possessed the higher peak intensities, leading us to conclude that these

samples show the higher chain orientation degree. So, curcumin and chitin enhance the phase

separation behavior and also the soft segment mobility, which is responsible for enhancing

chain alignments as well.

121

Figure 4.24: X-ray diffractograms of pristine and blends of curcumin and chitin based

PUs, (KPU2, KPU3)) and (KPU10-KPU12)

122



Thermogravimetric analysis (TGA) is a very helpful technique to examine the degradation

process of PUs (Javni et al., 2000). Figure 4.25 showed the TGA curves of pristine curcumin,

chitin based PU (KPU2, KPU3) and also the blends of curcumin/chitin based polyurethanes

(KPU10-KPU12). Conventionally weight loss occurred in two prominent stages (between

200 °C to 300

°C and 300

°C -500

°C) due to loss of moisture and thermal degradation of

polymers. A high decomposition temperature was observed for KPU3 than KPU2. Indeed the

N-acetyl-D-glucosamine is the basic unit of chitin that enhances the thermal resistivity of

chitin molecule as compared to curcumin molecule (Moussian et al., 2005). An increase in

final decomposition temperature of pristine chitin based PU is observed owing to effective

interaction stability between chitin and polyurethane prepolymer. The decomposition

temperature of KPU3 is more than KPU2 due to crosslinking behavior of chitin molecule.

However the samples KPU10, KPU11 and KPU12 showed a relative decreasing trend in

decomposition temperature as the concentration of chitin decreased. The sample in which

large amount of chitin was used in the form of blends showed more crosslinking behavior as

compared to the sample in which less amount of chitin was used. The temperature value at

which 20% weight loss occurred of KPU2, KPU3, KPU10, KPU11 and KPU12 are 360 ºC,

400 ºC, 368

ºC, 377

ºC and 388

ºC respectively. The results of comparative study regarding

the thermal behavior of KPU2, KPU3, KPU10, KPU11 and KPU12 showed that the chitin

based samples of PU showed better thermal stability as compared to curcumin based PU

samples. TGA of PU blends indicated a better thermal stability with 1.5 M:0.5M of chitin and

curcumin respectively. TGA values provide an evidence of better thermal stability of KPU12

as compared to KPU10 and KPU11. The crystallinity of chitin is due to N-acetyl-D-

glucosamine structure (Chen et al., 2004). Secondly in blended form chitin increases the

stability and thermal characters of synthesized material. Lundberg and Cox (1969) reported

that the PU with better crosslinking show better thermal stability.

123

Figure 4.25: TGA curves of polyurethane samples (KPU2, KPU3) and (KPU10-KPU12)

124

4.4.5.2 Differential scanning calorimetery (DSC) analysis

Figure 4.26 displays the DSC curves of pristine curcumin, chitin based PU (KPU2 & KPU3)

and curcumin/chitin blended PUs (KPU10-KPU12). The chemistry of polymer, crosslinking

of backbone chain, degree of crystallization and size of branching groups has a pronounced

effect on Tg values. The effect of chain extenders; chitin and curcumin in the backbone of

polyurethane material was examined by DSC analysis under same specifications or

conditions enlisted in previous section (4.2.5.2). The variation in thermal and crystalline

behavior of polyurethane elastomers was studied. By increasing the temperature from 25-625

°C, noticeable changes were observed in all polyurethane samples. From the figure 4.26 it has

been observed that thermal stability and crystallinity have been decreased by decreasing the

quantity of chitin as compared to curcumin. Curve of sample KPU3 showed more

crystallinity and thermal stability as compared to other samples of polyurethanes. The

chemical crosslinking also play its role for such thermally stable PU. Chitin developed

crosslinking with the backbone of PU, which enhanced its crystallinity and stability as

compared to curcumin based PU. On the other hand, stable keto-enol structure of curcumin

along with intermolecular hydrogen bonding with PU induces crystallinity but less than chitin

based PU. The DSC curves of KPU10, KPU11 and KPU12 showed that in blended samples,

the crystallinity and thermal stability are being increased by increasing the mole ratio of

chitin.

125

Figure 4.26: DSC curves of polyurethane samples (KPU2,KPU3) and (KPU10-KPU12)

126

4.4.6 Surface characterization

4.4.6.1 Assessment of water absorption percentage and equilibrium degree of swelling

The water absorption and swelling behavior (according to same procedure as mentioned in

previous section 4.2.6.1) are some of the physical characteristics which have been tested for

polyurethane materials and enlisted in table 4.7 and table 4.8. The data of table 4.7 showed

that the synthesized samples with greater concentration of chitin presented more hydrophobic

behavior as compared to the samples with lower concentration of chitin. On comparing the

effect of pristine chitin based PU and chitin-curcumin blended PUs, the result showed that

chitin based PU has lower water absorption tendency (due to chemical crosslinking behavior

of multi-functional chitin molecule) as compared to chitin-curcumin blended PUs. In the

blended form curcumin enhances the interaction of chitin with PU backbone. Therefore the

absorption properties of blended PU have been increased. The stable keto-enol structures of

curcumin along with intermolecular hydrogen bonding with PU make it more stable.

However, the stability is less than chitin blended PUs. Therefore, water absorption character

of curcumin based PU is higher as compared to chitin based PUs. The swelling behavior data

of prepared polyurethane samples is given in table 4.8, where the swelling behavior of

polyurethane elastomers have been decreased by increasing the quantity of chitin as

compared to curcumin in PU samples. The intermolecular hydrogen bonding and stable keto-

enol structure of curcumin reduces the swelling capability of polyurethane but this increment

is greater than chitin based PU samples.

Table 4.7: Water absorption of chitin/curcumin based polyurethane samples


Sample

code 0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU2 1.141 ±

0.04

1.163 ±

0.08

1.169 ±

0.06

1.171 ±

0.05

1.189 ±

0.02

1.199 ±

0.04

1.210 ±

0.05

1.214 ± 0.09

KPU3 1.161 ±

0.06

1.172 ±

0.02

1.179 ±

0.04

1.184 ±

0.09

1.188 ±

0.05

1.191 ±

0.06

1.192 ±

0.03

1.192 ± 0.02

KPU10 1.101 ±

0.07

1.123 ±

0.05

1.130 ±

0.08

1.136 ±

0.04

1.147 ±

0.03

1.149 ±

0.06

1.153 ±

0.04

1.158 ± 0.05

KPU11 1.081 ±

0.09

1.102 ±

0.02

1.109 ±

0.04

1.114 ±

0.07

1.115 ±

0.06

1.118 ±

0.08

1.122 ±

0.04

1.124 ± 0.03

127

KPU12 1.091 ±

0.08

1.107 ±

0.06

1.111 ±

0.05

1.116 ±

0.04

1.119 ±

0.07

1.122 ±

0.08

1.124 ±

0.05

1.127 ± 0.06



Table 4.8: Swelling behavior of chitin/curcumin based PU samples

Sample

number

Sample

code

Density

(g/cc)


degree of

swelling

(1/vR)a

0 day*

1st day 3

rd day 5

th day 7

th day

1 KPU2 1.044 1.30 1.74 1.84 1.89 1.87 1.97 ± 0.07

2 KPU3 1.064 1.26 1.65 1.70 1.68 1.66 1.60 ± 0.12

3 KPU10 1.058 1.22 1.62 1.70 1.73 1.71 1.73 ± 0.02

4 KPU11 1.060 1.30 1.71 1.78 1.81 1.77 1.66 ± 0.13

5 KPU12 1.062 1.32 1.74 1.80 1.79 1.77 1.62 ± 0.11



128

Part-V

4.5 Molecular, Thermal and Surface Characterization of Chitin / Clay,

Curcumin / Clay and BDO / Clay Based Polyurethane Elastomers and Bio-

nanocomposites.


Optimization of synthetic condition for HTPB, clay and HMDI results in NCO terminated PU

prepolymer bio-nanocomposite. Figure 4.27a represented the FTIR spectrum of PU bio-

nanocomposite prepolymer. The absence of characteristic OH peak and decrease in the

intensity of NCO peak confirms the reaction between NCO and OH group of polyol. The

peak at 3344.22 cm-1

due to NH group also confirms the formation of prepolymer. The

characteristic peaks in the spectrum of prepolymer in this case are in the similar region but

with different wave numbers as described in previous sections (4.2.1), i.e. CH2 asymmetric

stretching peak at 2930.44 cm-1

; symmetric stretching of CH2 peak at 2849.66 cm-1

; NCO


; carbonyl group peak at 1728.47 cm-1

; and CH2 bending peak at

1433.22 cm-1

. The NCO peak in spectrum confirmed the isocyanate terminated prepolymer

bio-nanocomposite.

Figure 4.27b (the spectrum of BDO / clay (0.1%) based polyurethane ) presented the

following peaks: the peak at 3351.23 cm-1

(NH group); 2944.11 cm-1

(CH2 asymmetric) ;

2823.73 cm-1

(CH2 symmetric); 1733.88 cm-1

(C═O group); 1578.21 cm-1

and 1529.75 cm-

1(NH deformation) and at 1219.55 cm

-1 (C─O elongating). In figure 4.27c (the spectrum of

curcumin / clay (0.1%) based polyurethane) showed the same functional group peaks with

different wave numbers such as; 3349.55 cm-1

, 2967.28 cm-1

, CH2 symmetric 2867.34 cm-1

;

C═O 1722.77 cm-1

; 1559.66 cm-1

, 1526.99 cm-1

, 1219.45 cm-1

for NH group, CH2

asymmetric and symmetric stretch, carbonyl, NH deformation and C─O bending. In figure

4.27d (the spectrum of chitin / clay (0.1%) based polyurethane) exhibited the following the

peaks at 3356.55 cm-1

(─NH group), at 2933.77 cm-1

(asymmetric CH2), at 2866.55 cm-1

(symmetric CH2), at 1733.63 cm-1

(C═O), 1584.18 cm-1

, 1552.45 cm-1

(NH deformation) and

1231.19 cm-1

(C─O). Analysis of FTIR in figure 4.27b, 4.27c & 4.27d showed that absence

of ─NCO peak and appearance of the broad N─H band confirmed the completion of reaction

and the peaks between 3305–3355 cm-1

endorse the presence of N─H stretching (Williams &

Flemming, 2006).

129


polyurethane structure: (a) PU prepolymer, (b) 1,4-butane diol / clay (0.1%) based

polyurethane, (c) curcumin / clay (0.1%) based polyurethane and (d) chitin / clay (0.1%)

based polyurethane

130


SEM is an analytical technique which is employed to monitor the formation of composites,

microstructure of intercalated clays and the compatibility between two kinds of polymers. It

is also helpful to study the topography. The surface morphology of synthesized polyurethane

elastomers (KPU1-KPU3) and bio-nanocomposites (KPU1/clay-KPU3/clay) were studied

and compared by using SEM images in figure 4.28. By using the clay in

BDO/curcumin/chitin based polyurethane samples the smoothness, stability increased and

cracking behavior decreased. In SEM image KPU3 and KPU3-clay (Figure 4.28) it has been

shown that there might be physical crosslinking which take place resulting in ordered pattern

i.e, crystallization region can be seen. In the samples KPU1-clay, KPU2-clay, and KPU3-

clay, the clay particles are fully dispersed with no agglomeration in final synthesized product

as depicted images. By adding the clay in KPU1, KPU2, KPU3 samples, the ordered pattern

and crystallization regions have become more prominent in contrast to neat KPU1 and KPU2

samples. From these results the participation of clay material into the polyurethane

prepolymer has been confirmed which has the ability to form ordered pattern. The ultimate

interaction between polyurethane prepolymer to that of chitin/curcumin/BDO/clay results in

change in the surface microstructure with subsequent dissimilar surface. In addition, no

agglomerations of curcumin, chitin and BDO have been observed with clay, confirming the

successful synthesis of homogeneous bio-nanocomposites.

131

Figure 4.28: SEM images of chitin, curcumin and BDO based polyurethane, elastomers

(KPU1-KPU3) and bio-nanocomposites (KPU1/clay-KPU3/clay)

132

4.5.3 X-Ray diffraction analysis

The clay dispersion within chitin, curcumin and BDO based polyurethanes has been

characterized by XRD, which is the most frequently used and approachable methods to study

the structure of nanocomposites. Depending on the relative distribution/dispersion of the

stacks of clay platelets, three types of PLSN have been described (Alexandre & Dubois,

2000; Ray & Okamoto, 2003). Intercalated PLSNs, where polymer chains are intercalated

into the silicate layers resulting in a well ordered mutilayer morphology built up with

alternating polymer and inorganic layers. Flocculated PLSNs, where intercalated stacked

silicate layers are sometime flocculated due to the hydroxylated edge–edge interactions. The

exfoliated/delaminated PLSNs, where the silicate layers are completely homogenously

dispersed in the polymer matrix. There are one acetamide (─NHCOCH3) group at C─2

position and two (02 hydroxy (─OH) groups at C─3 (C3─OH) and C─6 (C6─OH) positions

on chitin chains which can serve as the coordination and reaction sites (Zia et al., 2008).

Because of the polyfunctionality of chitin, it is suggested that this biopolymer can easily

intercalate in Na+-montmorillonite into the inter layers by means of cationic exchange

method. Madusanka et al. (2015) reported that (carboxymethyl cellulose/clay/curcumin)

nanocomposites showed increased crystallinity pattern by increasing clay quantity. Zia et al.

(2010) reported that the addition of bentonite nanoclay has changed the crystalline pattern.

The intensity of the crystalline peaks increases by adding bentonite nanoclay contents in PU

bio-nanocomposites, as supported by the XRD patterns. In figure 4.29 the comparative XRD

patterns of pristine BDO, curcumin, chitin based PUs elastomers (KPU1-KPU3) and

BDO/clay, curcumin/clay, chitin/clay based PU bio-nanocomposites (KPU1/clay-KPU3/clay)

are presented. The literature supports the idea that the well oriented crystallinity can be

observed at about 2θ = 20°. The 2θ values of crystalline peaks of KPU1, KPU1/clay, KPU2,

KPU2/clay, KPU3, KPU3/clay are 15.5°, 16

°, 17.5

°, 18.2

°, 21

°, 22

° respectively. From the

Figure 4.29 it has been cleared that by varying the chain extenders and adding the clay

particles the crystallinity patterns are being changed. If we compare the intensity of peaks of

samples with and without clay one can find that by using clay the crystallinity patterns are

upgraded.

133

Figure 4.29: X-ray diffractograms of pristine curcumin, chitin and BDO based PUs,

(KPU1-KPU3) and curcumin, chitin, BDO and clay based PU bio-nanocomposites


134


4.5.4.1 Thermogravimetric (TGA) analysis


process of renewable polyurethanes (Javni et al., 2000). Figure 4.30 showed the TG curves of

pristine BDO, curcumin, chitin, based PUs respectively (KPU1-KPU3) and blends of

BDO/clay, curcumin/clay, chitin/clay based polyurethane bio-nanocomposites (KPU1/clay-

KPU3/clay). A higher decomposition temperature was observed for clay incorporated

polyurethane bio-nanocomposites than without clay polyurethanes. The temperature values at

which 20% weight loss occurred i.e, KPU1, KPU1-clay, KPU2, KPU2-clay, KPU3 and

KPU3-clay are 325 ºC, 335

ºC, 360

ºC, 372

ºC, 400

ºC and 415

ºC respectively.

In the present work a comparative study has been reported to know the effect of clay on

BDO, curcumin and chitin based polyurethanes regarding thermal stability. An increase in

final decomposition temperature of clay based PU is observed owing to effective interaction

stability between BDO, curcumin, chitin and polyurethane prepolymer. In figure 4.30 we can

observe that the sample KPU1-clay showed more thermal stability as compared to sample

KPU1 in which clay was not being used. Such behavior can also be observed in samples

KPU2-clay, KPU2, KPU3-clay, KPU3 which shows that by the addition of clay the thermal

properties of synthesized polyurethane samples has been improved. Therefore, it can be

concluded that the clay enhance the intractability of polyurethane samples this can increase

the stability of synthesized samples which interns enhance the thermal decomposition

temperature accordingly. Finally, it can be concluded that TG values of KPU1-caly (335 ºC),

KPU2-clay (372 ºC) and KPU3-clay (415

ºC) have been improved as compared to the

samples which have been prepared without using clay such as KPU1 (325 ºC), KPU2 (360

ºC)

and KPU3 (400 ºC) etc.

135

Figure 4.30: TGA curves of polyurethanes samples (KPU1/clay-KPU3/clay) and (KPU1-

KPU3)

136


Figure 4.31 displays the DSC curves of BDO/clay, curcumin/clay, chitin/clay blended

(KPU1/clay-KPU3/clay) and without clay samples (KPU1-KPU3). DSC technique was

implied to examine the crystallinity and heat fluctuation of synthesized chitin/curcumin/BDO

based PU samples by using an instrument SDT Q 600 V20.9 Build 20. The effect of chain

extenders chitin, curcumin and BDO in the backbone of HTPB/clay/HMDI and HTPB/HMDI

induced polyurethane composite and elastomer materials were examined. The variation in

thermal and crystalline behavior of polyurethane composites and elastomers were studied. A

prominent change is seen by increasing the temperature from 25°C-625

°C in all polyurethane

samples. The KPU1/clay-KPU3/clay showed increase in thermal stability and crystallinity by

using the clay with chain extenders than without clay samples (KPU1, KPU2 and KPU3).

Intensity of damping peak decreases with increasing degree of crystallinity (Myrayama,

1978), therefore it can be inferred that by using nanoclay contents in chitin, curcumin and

BDO based polyurethanes, the crystalline pattern of the synthesized bio-nanocomposites

samples can be enhanced certainly.

137

Figure 4.31: DSC curves of polyurethane bio-nanocomposite samples (KPU1/clay-

KPU3/clay) and elastomers (KPU1-KPU3)

138


4.5.5.1 Assessment of water absorption and balance degree of swelling

The synthesized BDO/clay, curcumin/clay, chitin/clay based polyurethane elastomers and

bio-nanocomposites samples were immersed in water for seven days in order to understand

the physical behavior of samples such as water absorption tendency. The data after each day

was calculated and it is presented in table 4.9. The data that describes the samples in which

clay was used, presented more hydrophilic behavior as compared to the samples without clay.

On comparison the effect of pristine BDO, curcumin, chitin based PU and BDO/clay,

curcumin/clay and chitin/clay blended PU, the data shows that clay based PU has more water

absorption character as compared to pristine BDO, curcumin and chitin based PU sample. In

the blended form clay enhance the interaction of BDO, curcumin and chitin with PU

backbone. Therefore, the absorption properties of blended samples have been increased. A

possible explanation for such an improvement is the creation of a three-dimensional network

of interconnected long silicate layers which enhance the surface area of synthesized samples

leading to the improvement of the water absorption tendency as well. The swelling behavior

increased by using the clay in BDO, curcumin and chitin based PU samples as shown in table

4.10. The clay particles enhance the intractability of PU prepolymer with BDO, curcumin and

chitin which ultimately increase the swelling characters of synthesized materials. The

aqueous immersion and swelling actions of BDO, curcumin and chitin based polyurethane

has been increased by using the clay. Additionally, chitin/curcumin/BDO/clay blended

polyurethane possessed more functional physical properties as compared to pristine chitin,

curcumin and BDO based PU and can be suggested as a good biofunctional material.

139

Table 4.9: Water absorption of chitin/curcumin/BDO/clay based polyurethane samples


Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU1 1.310 ±

0.05

1.320 ±

0.07

1.328 ±

0.04

1.334 ±

0.02

1.339 ±

0.06

1.343 ±

0.08

1.345 ±

0.09

1.346 ± 0.07

KPU1-

clay

1.310 ±

0.08

1.331 ±

0.05

1.339 ±

0.03

1.356 ±

0.07

1.361 ±

0.09

1.366 ±

0.04

1.377 ±

0.06

1.388 ± 0.08

KPU2 1.340 ±

0.06

1.352 ±

0.08

1.360 ±

0.05

1.366 ±

0.03

1.371 ±

0.07

1.375 ±

0.04

1.377 ±

0.02

1.378 ± 0.06

KPU2-

clay

1.340 ±

0.07

1.373 ±

0.08

1.391 ±

0.05

1.398 ±

0.07

1.412 ±

0.04

1.427 ±

0.06

1.437 ±

0.04

1.449 ± 0.05

KPU3 1.360 ±

0.09

1.371 ±

0.05

1.378 ±

0.06

1.383 ±

0.04

1.387 ±

0.07

1.390 ±

0.08

1.391 ±

0.03

1.391 ± 0.05

KPU3-

clay

1.360 ±

0.07

1.382 ±

0.05

1.399 ±

0.08

1.415 ±

0.02

1.418 ±

0.05

1.441 ±

0.07

1.452 ±

0.06

1.452 ± 0.07



140

Table 4.10: Swelling actions of chitin/curcumin/BDO/clay based polyurethane samples

Sample

number

Sample code Density

(g/cc)


degree of

swelling

(1/vR)a

0 day*

1st day 3

rd day 5

th day 7

th day

1 KPU1 1.026 1.22 1.69 1.96 2.08 2.05 2.01 ± 0.11

2 KPU1-clay 1.024 1.22 1.73 2.01 2.14 2.16 2.06 ± 0.09

3 KPU2 1.035 1.20 1.64 1.74 1.79 1.77 1.87 ± 0.08

4 KPU2-clay 1.033 1.20 1.69 1.80 1.86 1.88 1.91 ± 0.12

5 KPU3 1.055 1.18 1.57 1.62 1.60 1.58 1.52 ± 0.14

6 KPU3-clay 1.053 1.18 1.60 1.66 1.68 1.68 1.55 ± 0.15



141

Part-VI


Curcumin / BDO and Chitin / Curcumin / BDO / Clay Blends Based

Polyurethane Elastomers and Bio-nanocomposites.


The primary discussion about PU prepolymer and its major function moieties from FTIR has

already been elaborated in previous section. Figure 4.32 presented the spectrum of BDO,

curcumin, chitin and clay blends based polyurethane. The figure 4.32b (spectrum of BDO

(50%) / curcumin (25%) / chitin (25%) / clay (0.1%) based polyurethane) present following

peaks at 3355.22 cm-1

(NH group); 2933.22 cm-1

(CH2 asymmetric); 2833.55 cm-1

(CH2

symmetric); 1716.66 cm-1

(C═O group); 1577.28 cm-1

, and 1544.77 cm-1

(NH deformation);

and 1230.44 cm-1

(C─O). The figure 4.32c (spectrum of BDO (25%) / curcumin (50%) /

chitin (25%) / clay (0.1%) based polyurethane) present peaks at wavenumbers such as

3355.33 cm-1

; 2942.66 cm-1

; 2866.33 cm-1

; 1740.44 cm-1

; 1568.33 cm-1

and 1541.66 cm-1

;

C─O at 1233.47 cm-1

with the same functions groups. In figure 4.32d (spectrum of BDO

(25%) / curcumin (25%) / chitin (50%) / clay (0.1%) based polyurethane) following peaks at

wavenumbers 3347.33 cm-1

; 2955.42 cm-1

; 2866.22 cm-1

; 1733.77 cm-1

; 1569.45 cm-1

, and

1550.58 cm-1

; and at 1218.37 cm-1

have been appeared.

142

Figure 4.32: FTIR spectra of PU prepolymer and final PU to confirms the proposed

polyurethane structure: (a) PU prepolymer, (b) BDO (50%) / curcumin (25%) / chitin

(25%) / clay (0.1%) based polyurethane, (c) BDO (25%) / curcumin (50%) / chitin

(25%) / clay (0.1%) based polyurethane and (d) BDO (25%) / curcumin (25%) / chitin

(50%) / clay (0.1%) based polyurethane

143


In order to monitor the formation of composites and microstructure of intercalated clays, the

SEM analysis is performed. The surface morphology of synthesized polyurethane elastomers

(KPU4-KPU6) and bio-nanocomposites (KPU4/clay-KPU6/clay) in figure 4.33 gives the

information about the incorporation of chitin/curcumin/BDO in prepared PU samples. In

SEM image of KPU6 and KPU6-clay (Figure 4.33), it is clearly shown that there might be

physical crosslinking took place which as an ordered pattern. The crystallization region can

be seen with smooth surface and less cracking. In the samples KPU4-clay, KPU5-clay and

KPU6-clay it has been cleared that the clay particles are fully dispersed without

agglomeration in final synthesized sample. In case of KPU4 and KPU5 samples (Figure 4.33)

decreasing mole ratio of chitin decreases this character as well. The ordered pattern and

crystallization regions have been observed prominently in clay based samples.

144

Figure 4.33: SEM images of blend of chitin, curcumin, BDO and clay based

polyurethanes, (KPU4-KPU6) and (KPU4/clay-KPU6/clay).

145

4.6.3 X-Ray Diffraction Analysis

The XRD pattern of curcumin, chitin and BDO blended PUs, (KPU4-KPU6) and curcumin,

chitin, BDO and clay blends based PU bio-nanocomposites (KPU4/clay-KPU6/clay)

exhibited strong scattering peaks at 2θ angles between 15-22°

(Figure 4.34). Polymer

nanocomposite is a class of hybrid materials composed of an organic polymer matrix with

dispersed inorganic nanofillers, which have at least one dimension in nanometer range

(Giannelis, 1996). At this scale, the large surface area of the nanofiller, even at very low

concentration, can markedly change the macroscopic properties of the polymer and contribute

many new characteristics to the polymer, such as increased crystallinity. The figure 4.34

presented the comparative study of XRD pattern of polyurethane elastomers and bio-

nanocomposites. From the XRD pattern it became evident that by changing the chain

extenders and adding the clay (nanofillers), the intensity of peak and 2θ value both have been

changed. As discussed earlier (section 4.5.3), the reported work shows that by increasing the

mole ratio of chitin or adding clay the crystallinity of synthesized samples was improved. The

2θ values of KPU4, KPU4/clay, KPU5, KPU5/clay, KPU6, KPU6/clay are 15.8°, 16.5

°, 16.8

°,

17.8°, 18.5

°, and 19.5

° respectively. All samples presented crystallinity behavior due to

aliphatic diisocyanate (HMDI to prepare prepolymer) structure, but due to different chain

extenders and by the addition of clay particles different intensities of peaks at different 2θ

values were observed. The reported literature showed that the well oriented crystallinity have

been observed at about 2θ = 20°. Therefore, by varying the chain extenders and adding the

clay particles the crystallinity patterns can be changed. On comparison, the intensity of peaks

of samples with and without clay it can be observed that by the addition of clay the

crystallinity patterns are better.

146

Figure 4.34: X-ray diffractograms of curcumin, chitin and BDO blended PUs, (KPU4-

KPU6) and curcumin, chitin, BDO and clay blends based PU bio-nanocomposites


147

4.6.4 Thermal analysis



process of renewable established PUs (Javni et al., 2000). Figure 4.35 showed the TG curves

of BDO (50%) / curcumin (25%) / chitin (25%), BDO (25%) / curcumin (50%) / chitin

(25%), BDO (25%) / curcumin (25%) / chitin (50%) blends based PU elastomers

respectively (KPU4-KPU6) and blends of BDO (50%) / curcumin (25%) / chitin (25%) / clay

(0.1%), BDO (25%) / curcumin (50%) / chitin (25%) / clay (0.1%), BDO (25%) / curcumin

(25%) / chitin (50%) / clay (0.1%) based polyurethane bio-nanocomposites (KPU4/clay-

KPU6/clay). The TGA curves show the weight loss in two prominent stages between 200 ˚C

to 300 ˚C and 300 ˚C -500 °C due to loss of moisture and thermal degradation of polymers.

The value of temperature at which 20% weight loss occurred of KPU4, KPU4-clay, KPU5,

KPU5-clay, KPU6 and KPU6-clay are 365 ºC, 377

ºC, 375

ºC, 388

ºC, 385

ºC and 400

ºC

respectively. A comparative study was reported to know the effect of clay on BDO,

curcumin and chitin based polyurethanes regarding thermal stability. An increase in final

decomposition temperature of clay based PU is observed owing to active interaction stability

between BDO, curcumin, chitin and polyurethane prepolymer. The samples KPU4-clay,

KPU5-clay, and KPU6-clay showed more improved thermal stability as compared to KPU4,

KPU5 and KPU6. Clay actually enhanced the intractability of polyurethanes proposing

increased stability which enhance the thermal decomposition temperature accordingly.

148

Figure 4.35: TGA curves of polyurethane samples (KPU4/clay-KPU6/clay) and (KPU4-

KPU6)

149


The DSC curves of BDO (50%) / curcumin (25%) / chitin (25%), BDO (25%) / curcumin

(50%) / chitin (25%), BDO (25%) / curcumin (25%) / chitin (50%) blends based PU

elastomers respectively (KPU4-KPU6) and blends of BDO (50%) / curcumin (25%) / chitin

(25%) / clay (0.1%), BDO (25%) / curcumin (50%) / chitin (25%) / clay (0.1%), BDO (25%)

/ curcumin (25%) / chitin (50%) / clay (0.1%) based polyurethane bio-nanocomposites

(KPU4/clay-KPU6/clay) are shown in figure 4.36. The DSC thermograms were taken under

the same conditions as mentioned above to evaluate the glass transition temperature (Tg),

crystallization temperature (Tc), melting tempreture (Tm) and decomposition temperature (Td)

of samples. Effect of chain extenders; chitin, curcumin, BDO in the backbone of

HTPB/clay/HMDI centered polyurethane elastomers and bio-nanocomposites material were

examined and the notable change in thermal and crystalline behavior of polyurethane

samples was discussed. An obvious change in PU samples is studied by increasing the

temperature from 25 °C-625

°C. Here in, (Figure 4.36) one can observe the higher thermal

stability and crystallinity of KPU4-clay-KPU6-clay as compared to samples KPU4-KPU6

without using clay.

150

Figure 4.36: DSC curves of polyurethane bio-nanocomposites (KPU4/clay-KPU6/clay)

and elastomers (KPU4- KPU6)

151



The physical tests were carried out in order to understand the hydrophilic character of

synthesized PU materials i.e., the percentage of H2O absorption and degree of swelling (in

some suitable solvent) is reported in table 4.11 and table 4.12. From the data it can be

observed that the amount of water absorption does not depend on the duration of time but on

the nature or type of chain extender BDO, curcumin, chitin and clay. A more hydrophilic

behavior in clay blended PU is observed as compared to samples without clay

(BDO/curcumin/chitin based PU). The blends form with clay improve the interaction of

BDO/curcumin/chitin with PU backbone, therefore the absorption properties were increased

due to the creation of a three-dimensional network of interconnected long silicate layers

which enhance the surface area of synthesized samples, improving the absorption properties.

The swelling behavior results of prepared clay based blended polyurethane elastomer and

composite samples are shown in table 4.12, where increase in swelling level is seen by using

the clay in BDO, curcumin and chitin based PU samples than neat (without clay) ones due to

more pronounced intractability of clay between PU prepolymer and BDO, curcumin and

chitin which ultimately increase the swelling characters of synthesized materials and can be

considered as a good biofunctional material.

152

Table 4.11: Water absorption of BDO/chitin/curcumin/clay based polyurethane samples


Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU4 1.120 ±

0.06

1.132 ±

0.03

1.139 ±

0.07

1.145 ±

0.02

1.149 ±

0.09

1.152 ±

0.06

1.154 ±

0.04

1.155 ± 0.03

KPU4-

clay

1.120 ±

0.09

1.143 ±

0.05

1.150 ±

0.06

1.156 ±

0.08

1.171 ±

0.05

1.175 ±

0.07

1.180 ±

0.08

1.187 ± 0.04

KPU5 1.100 ±

0.07

1.111 ±

0.04

1.118 ±

0.02

1.123 ±

0.07

1.127 ±

0.05

1.130 ±

0.08

1.131 ±

0.09

1.132 ± 0.05

KPU5-

clay

1.100 ±

0.08

1.132 ±

0.06

1.139 ±

0.05

1.155 ±

0.09

1.158 ±

0.04

1.171 ±

0.04

1.193 ±

0.06

1.195 ± 0.07

KPU6 1.110 ±

0.04

1.121 ±

0.07

1.128 ±

0.08

1.133 ±

0.02

1.137 ±

0.08

1.140 ±

0.05

1.141 ±

0.06

1.141 ± 0.09

KPU6-

clay

1.110 ±

0.06

1.132 ±

0.05

1.139 ±

0.03

1.144 ±

0.07

1.148 ±

0.09

1.162 ±

0.05

1.162 ±

0.08

1.162 ± 0.06



153

Table 4.12: Swelling behavior of BDO/chitin/curcumin/clay based PU samples

Sample

number

Sample code Density

(g/cc)


degree of swelling

(1/vR)a 0 day

* 1

st day 3

rd day 5

th day 7

th day

1 KPU4 1.047 1.111 1.511 1.591 1.621 1.601 1.621 ± 0.09

2 KPU4-clay 1.046 1.111 1.532 1.622 1.662 1.652 1.632 ± 0.12

3 KPU5 1.049 1.181 1.601 1.671 1.701 1.681 1.551 ± 0.08

4 KPU5-clay 1.048 1.181 1.622 1.702 1.742 1.732 1.562 ± 0.10

5 KPU6 1.051 1.212 1.631 1.691 1.681 1.671 1.511 ± 0.11

6 KPU6-clay 1.050 1.212 1.662 1.722 1.712 1.702 1.532 ± 0.15



154

Part-VII

4.7 Molecular, Thermal and Surface Characterization of Curcumin / BDO

and Curcumin / BDO / Clay Blends Based Polyurethane Elastomers and

Bio-nanocomposites.


HTPB/clay and HMDI were treated for one hour at 100 °C to prepare NCO ended PU

prepolymer bio-nanocomposite. Figure 4.37a showed the FTIR spectrum of PU prepolymer

bio-nanocomposite. In the spectrum of prepolymer bio-nanocomposite the peak of OH is not

appeared and also the intensity of NCO group has been decreased significantly. The data has

been observed that the reaction between NCO and OH group of polyol occurred. Resulting in

the peak at 3328.64 cm-1

in spectrum, which is due to NH group, the indication of NH group

in prepolymer confirmed that the process of prepolymer formation. The appeared peaks in

polyurethane prepolymer spectrum are due to: CH2 asymmetric stretching at 2934.48 cm-1

;

symmetric stretching of CH2 at 2862.59 cm-1

; NCO peak at 2266.47 cm-1

; carbonyl group


; and CH2 bending showed value at 1438.24 cm-1

. The NCO peak in

spectrum confirmed that isocyanate terminated PU prepolymer bio-nanocomposite has been

formed. In order to obtain a final polymer, synthesized prepolymer is extended with different

chain extenders that are curcumin and BDO blends were used. Figure 4.37 presented the

spectrum of BDO, curcumin, clay based polyurethane. In figure 4.37b the spectrum of BDO

(75%) / curcumin (25%) / clay (0.1%) based polyurethane is presented, which showed the


is due to NH group; due to CH2 asymmetric peak

showed at 2933.55 cm-1

, CH2 symmetric presented peak at 2833.77 cm-1

, carbonyl group in

spectrum showed value at 1719.66 cm-1

, NH deformation presented peaks at 1575.23 cm-1

,

1529.67 cm-1

, C─O elongating peak was observed at 1215.55 cm-1

. In figure 4.37c the

spectrum of BDO (50%) / curcumin (50%) / clay (0.1%) based polyurethane is presented,

which presented the following peaks: the peak at 3329.30 cm-1

is due to NH group, due to

CH2 asymmetric peak showed at 2941.47 cm-1

, CH2 symmetric presented peak at 2848.37

cm-1

, C═O group peak was observed at 1746.54 cm-1

, NH deformation showed peaks at

1581.31 cm-1

, 1542.62 cm-1

, C─O elongating peak was observed at 1230.42 cm-1

. In figure

4.37d the spectrum of BDO (25%) / curcumin (75%) / clay (0.1%) based polyurethane is

presented, spectrum showed the following peaks: the peak at 3344.39 cm-1

is due to NH

group; due to CH2 asymmetric peak appeared at 2939.70 cm-1

; hydrocarbon symmetric peak

155


; C═O group peak has been observed at 1731.99 cm-1

; NH

deformation showed peaks at 1569.57 cm-1

, 1537.74 cm-1

; C─O elongating peak was

observed at 1219.19 cm-1

.


polyurethane structure: (a) PU prepolymer, (b) BDO (75%) / curcumin (25%) / clay

(0.1%) based polyurethane, (c) BDO (50%) / curcumin (50%) / clay (0.1%) based

polyurethane and (d) BDO (25%) / curcumin (75%) / clay (0.1%) based polyurethane

bio-nanocomposites

156


Compatibility of two kinds of polymers, composition and surface topography has been

explained by SEM analysis. The surface morphology of synthesized polyurethane elastomer

samples (KPU7-KPU9) are presented in figure 4.38. These images give the information about

the incorporation of curcumin/BDO in prepared PU prepolymer elastomer and bio-

nanocomposite samples. By using the clay in BDO/curcumin based polyurethane samples

enhance the smoothness, stability and decreased the cracking behavior. In SEM image KPU9

and KPU9-clay (Figure 4.38), it is clearly shown that there might be physical stability that

can be observed and possessed ordered pattern that is crystallization region can be observed.

Secondly from the sample KPU9-clay it has been found that the clay particles are fully

dispersed in final synthesized sample. While in SEM images KPU7 and KPU8 (Figure 4.38)

have showed a decrease in such behavior due to decreasing mole ratio of curcumin. The SEM

images of KPU7-clay and KPU8-clay showed that the clay particles are fully dispersed and

no agglomeration is found between clay and polyurethanes. By adding the clay in KPU7,

KPU8, KPU9 samples (Figure 4.38) the ordered pattern and crystallization regions are more

prominent. From these results the participation of clay material into the polyurethane

prepolymer has been confirmed which has the ability to form ordered pattern. Surface

microstructure has been changed and the subsequent dissimilar surface is due to final

interaction between polyurethane prepolymer with that of curcumin/BDO/clay. No

agglomerations of curcumin and BDO with clay have been seen, confirming the successful

synthesis of a homogeneous bio-nanocomposites and elastomers.

157

Figure 4.38: SEM images of blend of curcumin and BDO based polyurethane

elastomers, (KPU7-KPU9) and polyurethane bio-nanocomposites (KPU7/clay-

KPU9/clay)

158

4.7.3 X-Ray Diffraction Studies

To understand the physical nature of curcumin/BDO and curcumin/BDO/clay with in the PU

backbone, XRD pattern (Figure 4.39) of curcumin/BDO based elastomers and

curcumin/BDO/clay based bio-nanocomposites were compared. Out of many available

nanomaterials, clay particularly montmorillonite (MMT), consisting of the stacks of alumina

silicate layers which occur in nanometer scale in thickness with interlayer charge balancing

ions, have attracted considerable attention due to their potential applications in the synthesis

of nanocomposites based on organic/inorganic materials that have properties of both

inorganic host and organic guest in a single system (Ray &Okamoto, 2003). Madusanka et al.

(2015) reported that (carboxymethyl cellulose/clay/curcumin) nanocomposites showed

increased crystallinity pattern by increasing clay quantity. The C═C in the curcumin increase

the phase separation as compared to BDO which ultimately allowed the soft segments for

alignments of chain. In figure 4.39 the comparative XRD patterns of BDO, curcumin blended

PUs elastomers (KPU7-KPU9) and BDO/curcumin/clay blended PU bio-nanocomposites

(KPU7/clay-KPU9/clay) are presented. As HMDI give crystalline behavior to prepared

samples, but by changing the chain extenders and adding clay crystallinity is changed. The 2θ

values of crystalline peaks of KPU7, KPU7/clay, KPU8, KPU8/clay, KPU9, KPU9/clay are

16°, 16.5

°, 16.4

°, 16.9

°, 17.2

°, 18.5

° respectively. From the figure 4.39 it has been cleared that

by varying the chain extenders and adding the clay particles the crystallinity patterns are

changed.

159

Figure 4.39: X-ray diffractograms of curcumin and BDO blend based PUs, (KPU7-

KPU9) and curcumin, BDO and clay blends based PU bio-nanocomposites (KPU7/clay-

KPU9/clay)

160



TGA study is a very helpful technique to examine the degradation process of renewable

established PUs (Javni et al., 2000). Figure 4.40 showed the TGA curves of BDO (75%) /

curcumin (25%) / clay (0.1%), BDO (50%) / curcumin (50%) / clay (0.1%), BDO (25%) /

curcumin (75%) / clay (0.1%) PU bio-nanocomposites and BDO (75%) / curcumin (25%),

BDO (50%) / curcumin (50%), BDO (25%) / curcumin (75%) based polyurethane elastomers.

Weight loss occurred in two prominent stages as shown in TGA curves i.e., between 200 ˚C

to 300 ˚C (loss of moisture) and 300-500 °C (thermal degradation of polymers). Generally, a

prominent difference was noted in the second stage. The temperature value at which 20%

weight loss occurred of KPU7, KPU7-clay, KPU8, KPU8-clay, KPU9 and KPU9-clay are

335 ºC, 347

ºC, 342

ºC, 357

ºC, 350

ºC and 365

ºC respectively. A higher decomposition

temperature was observed for clay incorporated polyurethanes than without clay

polyurethanes. The keto-enol structure of curcumin makes it more stable and enhances its

intractability with polyurethane. Chen et al. (2014) reported two step decomposition of

curcumin primarily due to substituent group of curcumin and by the decomposition of

benzene rings. Sun et al. (2013) has reported that curcumin was decomposed at 194 ºC in

DSC curve. Conversely, Souguir et al. (2013) presented the TGA curve of curcumin weight

loss (1.344 %) at 190.88 ºC. In this work a comparative study was reported to understand the

effect of clay on BDO, curcumin based polyurethanes regarding thermal stability. An

increase in final decomposition temperature of clay based PU is observed owing to create

effective interaction stability between BDO, curcumin polyurethane prepolymer. In figure

4.40 we can observe that the sample KPU7-clay showed more thermal stability as compared

to sample KPU7 in which clay was not being used. Such behavior of increased thermal

stability by the addition of clay can also be observed in various samples such as KPU8-clay,

KPU8 and KPU9-clay, KPU9. Consequently, it can be stated that the clay enhance the

intractability of polyurethane samples, regarding the stability and enhancement in the thermal

decomposition temperature accordingly. Finally, it can be concluded that TGA values of

KPU7-caly, KPU8-clay and KPU9-clay have been improved as compared to polyurethane

samples without filler.

161

Figure 4.40: TGA curves of polyurethane bio-nanocomposites (KPU7/clay-KPU9/clay)

and polyurethane elastomers (KPU7-KPU9)

162


Figure 4.41 displayed the DSC curves of BDO (75%) / curcumin (25%), BDO (50%) /

curcumin (50%), BDO (25%) / curcumin (75%) blended elastomers (KPU7-KPU9)

respectively and blends of BDO (75%) / curcumin (25%) / clay (0.1%), BDO (50%) /

curcumin (50%) / clay (0.1%), BDO (25%) / curcumin (75%) / clay (0.1%) based

polyurethane bio-nanocomposites (KPU7/clay-KPU9/clay) respectively. The chemistry of

polymer, crosslinking of main chain, degree of crystallization and size of branching groups

effect on Tg value. During melting stage sample absorbs heat, and showed endotherm peak.

After weighing the samples, these were studied in temperature range from 25 ºC to 625

ºC at

the rate of 10 °C/min under N2 atmosphere. DSC analysis examined the effect of curcumin,

and BDO in the backbone of HTPB/clay/HMDI based polyurethane prepolymer elastomer

and bio-nanocomposite material. The thermal and crystalline change in behavior of

polyurethane samples was investigated by increasing the temperature from 25 °C-625

°C. An

evident change in all polyurethane samples as depicted from DSC thermograms i.e., thermal

stability and crystallinity of KPU7/clay-KPU9/clay (Figure 4.41) has been increased by using

the clay with chain extenders. Curve of samples KPU7-clay-KPU9-clay showed more

crystallinity and thermal stability as compared to samples without clay KPU7-KPU9. The

intensity of damping peak decreases with increasing degree of crystallinity (Myrayama,

1978) as reported previously. Therefore, it can be concluded that by using nanoclay contents

in curcumin and BDO based polyurethanes certainly enhance the crystalline pattern of the

synthesized bio-nanocomposite samples.

163


and PU elastomers (KPU7-KPU9)

164



The physical behavior such as H2O immersion and level of swelling of prepared polyurethane

elastomers and bio-nanocomposites material were calculated and enlisted in respective table

4.13 and table 4.14. Data after immersion of the BDO/curcumin/clay based polyurethane

samples in water for seven days (after each day) was recorded and it is presented in table

4.13. The data of table 4.13 showed that the synthesized samples, in which clay was used,

developed more hydrophilic character as compared to samples without clay. On comparing

the BDO/curcumin blended PU and BDO/curcumin/clay blended PU, better water absorption

character in clay based PU is noted when compared to BDO/curcumin based PU. Clay

actually enhances the interaction of BDO/curcumin with PU backbone, therefore the

absorption properties of blend based PU has been increased. This was probably due to

creation of a three-dimensional network of interconnected long silicate layers which enhance

the surface area of synthesized samples and thus ultimately improved the absorption

properties. The swelling behavior data of synthesized polyurethane elastomer and bio-

nanocomposite samples are given in table 4.14 where the swelling character of polyurethane

samples is increased by using the clay in BDO, curcumin based PU samples. In contrary to

that, synthesized polyurethane samples without clay has shown less swelling character as

compared to clay based polyurethane. The clay particles enhance the intractability of PU

prepolymer with BDO and curcumin which ultimately increase the swelling characters of

synthesized materials. Curcumin/BDO/clay blended polyurethane possessed unique physical

properties as compared to curcumin/BDO blended PU and can be suggested as a good

biofunctional material.

165

Table 4.13: Water absorption of BDO/curcumin/clay based polyurethane samples


Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU7 1.220 ±

0.09

1.230 ±

0.06

1.238 ±

0.05

1.244 ±

0.08

1.249 ±

0.07

1.253 ±

0.04

1.255 ±

0.03

1.256 ± 0.02

KPU7-

clay

1.220 ±

0.08

1.251 ±

0.07

1.269 ±

0.04

1.285 ±

0.06

1.310 ±

0.02

1.324 ±

0.04

1.346 ±

0.02

1.358 ± 0.03

KPU8 1.250 ±

0.07

1.262 ±

0.06

1.270 ±

0.04

1.276 ±

0.05

1.281 ±

0.03

1.285 ±

0.08

1.287 ±

0.03

1.288 ± 0.05

KPU8-

clay

1.250 ±

0.05

1.283 ±

0.03

1.291 ±

0.04

1.317 ±

0.07

1.342 ±

0.05

1.356 ±

0.06

1.368 ±

0.07

1.370 ± 0.04

KPU9 1.190 ±

0.07

1.201 ±

0.04

1.208 ±

0.06

1.213 ±

0.09

1.217 ±

0.06

1.220 ±

0.05

1.221 ±

0.06

1.222 ± 0.08

KPU9-

clay

1.190 ±

0.04

1.222 ±

0.06

1.239 ±

0.02

1.254 ±

0.04

1.278 ±

0.05

1.291 ±

0.07

1.322 ±

0.08

1.325 ± 0.06



166

Table 4.14: Swelling behavior of BDO/curcumin/clay based PU samples

Sample

number

Sample code Density

(g/cc)


degree of

swelling (1/vR)a 0 day

* 1

st day 3

rd day 5

th day 7

th day

1 KPU7 1.025 1.211 1.681 1.951 2.071 2.041 1.92 ± 0.09

2 KPU7-clay 1.023 1.211 1.703 1.984 2.135 2.127 1.97 ± 0.11

3 KPU8 1.034 1.191 1.631 1.731 1.781 1.761 1.82 ± 0.08

4 KPU8-clay 1.031 1.191 1.654 1.765 1.816 1.805 1.86 ± 0.10

5 KPU9 1.046 1.181 1.601 1.671 1.701 1.681 1.65 ± 0.11

6 KPU9-clay 1.043 1.181 1.632 1.693 1.742 1.733 1.68 ± 0.13



167

Part-VIII


Curcumin and Chitin / Curcumin / Clay Blends Based Polyurethane

Elastomers and Bio-nanocomposites.


Figure 4.42a represented the FTIR spectrum of PU prepolymer bio-nanocomposite. The

distinct peaks in PU prepolymer has already been described in previous section (4.5.1).

Figure 4.30 presented the spectrum of prepolymer bio-nanocomposite and

curcumin/chitin/clay blended polyurethane bio-nanocomposites. In figure 4.42b the spectrum

of curcumin (75%) / chitin (25%) / clay (0.1%) based polyurethane bio-nanocomposite is

presented, which showed the following peaks: the peak at 3333.76 cm-1

is due to NH group;

due to CH2 asymmetric peak appeared at 2943.55 cm-1

; CH2 symmetric appeared peak at

2854.56 cm-1

; carbonyl group in spectrum showed the value of 1734.65 cm-1

; NH

deformation showed the peaks at 1577.22 cm-1

, 1529.67 cm-1

; C─O peak was observed at

1221.49 cm-1

. In figure 4.42c the spectrum of curcumin (50%) / chitin (50%) / clay (0.1%)

based polyurethane bio-nanocomposite is presented, which depicted the following peaks: the


is due to NH group; due to CH2 asymmetric peak appeared at 2942.62

cm-1

; CH2 symmetric peak was observed at 2848.52 cm-1

; C═O group peak was observed at

1727.29 cm-1

; NH deformation peaks appeared at 1588.25 cm-1

, 1540.68 cm-1

; C─O peak

was observed at 1231.45 cm-1

. In figure 4.42d the spectrum of curcumin (25%) / chitin (75%)

/ clay (0.1%) based polyurethane bio-nanocomposite is presented, spectrum showed the


is due to NH group; due to CH2 asymmetric peak


; hydrocarbon symmetric was observed at 2849.29 cm-1

; C═O group

peak observed at 1734.77 cm-1

; NH deformation showed the peaks at 1556.22 cm-1

, 1539.55

cm-1

; C─O peak was observed at 1219.24 cm-1

. Analysis of FTIR in figure 4.42b, 4.42c &

4.42d showed that there is no ─NCO peak and the prominent broad peak of N─H confirmed

the completion of the reaction. The values of peaks in the region of 3305–3355 cm-1

endorse

the presence of N─H stretching (Williams & Flemming, 2006).

168


polyurethane structure: (a) PU prepolymer, (b) curcumin (75%) / chitin (25%) / clay

(0.1%) based polyurethane, (c) curcumin (50%) / chitin (50%) / clay (0.1%) based

polyurethane and (d) curcumin (25%) / chitin (75%) / clay (0.1%) based polyurethane

169


SEM analysis provides the information about the formation of composites and microstructure

of intercalated clays. The resulting images present the surface morphology of synthesized

polyurethane samples (KPU10-KPU12) and (KPU10/clay-KPU12/clay) in figure 4.43. These

images provide the information about the incorporation of curcumin/chitin in prepared PU

prepolymer bio-nanocomposite and elastomer samples. By using the clay in chitin/curcumin

based polyurethane samples smoothness, and stability is enhanced. However, the surface

cracking is decreased. The physical stability is reflected by the ordered pattern of

crystallization region in SEM image of KPU12 and KPU12-clay (Figure 4.43). From the

sample KPU12-clay it has been identified that the clay particles are fully dispersed in final

synthesized sample. While in SEM images of KPU10 and KPU11 (Figure 4.43) such

behavior is reduced, due to decreased mole ratio of chitin. The SEM images of KPU10-clay

and KPU11-clay have clearly manifested that the clay particles are fully dispersed and no

agglomeration is formed between clay and polyurethanes. The SEM images of blended PU

samples KPU10/clay-KPU12/clay (Figure 4.43) exhibited that by adding the clay in KPU10,

KPU11, KPU12 samples; the ordered pattern and crystallization regions became more

prominent. From the data, the participation of clay which has the ability to form ordered

pattern into the polyurethane prepolymer has been confirmed. In addition, no agglomerations

of curcumin and chitin have been observed with clay, which confirm the successful synthesis

of a homogeneous nanocomposites and elastomers.

170

Figure 4.43: SEM images of curcumin/chitin blend based polyurethane elastomers,

(KPU10-KPU12) and bio-nanocomposites (KPU10/clay-KPU12/clay)

171

4.8.3 X-Ray Diffraction analysis

The XRD technique was used to understand the effect of bentonite clay that has been

incorporated in the polymer hybrid to improve some targeted properties. In the present study

the effect of clay particles on the blend of chitin/curcumin polyurethanes were noted, and

compared without clay samples by using XRD technique. In chitin molecule there is one

acetamide (─NHCOCH3) group at C─2 position and two hydroxy (─OH) groups at C─3

(C3─OH) and C─6 (C6─OH) positions which act as reactive sites (Zia et al., 2008). Because

of the polyfunctionality of chitin, it is suggested that this biopolymer can easily intercalate in

Na+ montmorillonite into the inter layers by means of cationic exchange. Madusanka et al.

(2015) reported that (carboxymethyl cellulose/clay/curcumin) nanocomposites showed

increased crystallinity pattern by increasing clay quantity. In figure 4.44 the comparative

XRD patterns of curcumin, chitin blended PUs elastomers (KPU10-KPU12) and

curcumin/chitin/clay blended PU bio-nanocomposites (KPU10/clay-KPU12/clay) are given.

Commonly HMDI creates crystallinity due to its aliphatic nature. On the other hand by

changing chain extenders and adding clay particles showed different intensities of peaks at

different 2θ values. The reported literature showed that the well oriented crystallinity

observed at about 2θ = 20°. The 2θ values of crystalline peaks of KPU10, KPU10/clay,

KPU11, KPU11/clay, KPU12, KPU12/clay are 17.7°, 18.4

°, 18.6

°, 19.5

°, 20.2

°, 21.8

°

respectively. From the figure 4.44 it has been concluded that by varying the chain extenders

and clay particles crystallinity is affected while the peak intensity of samples with clay

particles showed the greater crystalline pattern.

172

Figure 4.44: X-ray diffractograms of curcumin, chitin blends based PUs, (KPU10-

KPU12) and curcumin/chitin and clay blends based PU bio-nanocomposites


173

4.8.4 Thermal characterization


Thermogravimetric (TG) study is a very helpful technique to examine the degradation

process of renewable established PUs (Javni et al., 2000). Figure 4.45 showed the TG curves

of curcumin (75%) / chitin (25%) / clay (0.1%), curcumin (50%) / chitin (50%) / clay (0.1%),

curcumin (25%) / chitin (75%) / clay (0.1%) based polyurethane bio-nanocomposites and

curcumin (75%) / chitin (25%), curcumin (50%) / chitin (50%), curcumin (25%) / chitin

(75%) based polyurethane elastomers. In TG curves weight loss occurred in two major

stages, between 200 to 300 ˚C, and 300-500 °C due to loss of moisture and thermal

degradation of polymers respectively. In first stage the weight loss rates are nearly equal. But

in second stage a noticeable difference was observed. The temperature value at which 20%

weight loss occurred of KPU10, KPU10-clay, KPU11, KPU11-clay, KPU12 and KPU12-clay

are 368 ºC, 382

ºC, 374

ºC, 395

ºC, 388

ºC and 410

ºC respectively. A higher decomposition

temperature was observed for clay incorporated polyurethanes than without clay. In case of

curcumin, Chen et al. (2014) reported that decomposition in curcumin occur due to the

substituent group followed by the decomposition of benzene rings in two stages. Curcumin

was decomposed at 194 °C in DSC curve while TG curve of curcumin presented weight loss

(1.344 %) at 190.88◦C (Souguir et al. 2013; Sun et al. 2013).

In this work a comparative study was reported to know the effect of clay on chitin,

curcumin based polyurethanes regarding thermal stability. An increase in the final

decomposition temperature of clay based PU is observed owing to create effective interaction

stability between chitin, curcumin polyurethane prepolymer bio-nanocomposite. In the figure

4.45 we can observe that the sample KPU10-clay showed more thermal stability as compared

to the sample KPU10 without clay. Such behavior can also be observed in samples KPU11-

clay, KPU11 and KPU12-clay, KPU12 that is by the addition of clay thermal properties of

synthesized polyurethane samples has been improved. Therefore, it can be stated that the clay

enhances the intractability of polyurethane samples, via this stability of synthesized samples

increased which enhance the thermal decomposition temperature accordingly. Finally, it can

be concluded that TGA values of KPU10-caly, KPU11-clay and KPU12-clay have been

improved as compared to polyurethane samples without clay.

174

Figure 4.45: TGA curves of polyurethane bio-nanocomposites (KPU10/clay-

KPU12/clay) and polyurethane elastomers (KPU10-KPU12)

175

4.8.4.2 Differential scanning calorimetery (DSC) analysis

Figure 4.46 displayed the DSC curves of curcumin (75%) / chitin (25%), curcumin (50%) /

chitin (50%), curcumin (25%) / chitin (75%) blended PU elastomers (KPU10-KPU12)

respectively and blends of curcumin (75%) / chitin (25%) / clay (0.1%), curcumin (50%) /

chitin (50%) / clay (0.1%), curcumin (25%) / chitin (75%) / clay (0.1%) based polyurethane

bio-nanocomposite (KPU10/clay-KPU12/clay) respectively. The effect of chain extenders

blends of curcumin/chitin in the backbone of HTPB/clay/HMDI centered polyurethane

elastomers and bio-nanocomposites material were examined by DSC analysis under the same

way and conditions as mentioned in previous section (4.5.4.2). The change in thermal and

crystalline behavior of polyurethane samples was studied by increasing the temperature from

25 °C-625

°C. From DSC thermograms of KPU10/clay-KPU12/clay showed glass transition

temperature (Tg), crystalline temperature (Tc) and melting temperature (Tm) peaks. From

figure 4.46 it has been observed that thermal stability and crystallinity have been increased by

using the clay with chain extenders. Curve of samples KPU10-clay-KPU12-clay showed

more crystallinity and thermal stability as compared to the samples without clay KPU10-

KPU12. It has also been previously reported that the intensity of damping peak decreases

with increasing degree of crystallinity (Myrayama, 1978). Therefore, it can be concluded that

using nanoclay contents in curcumin/chitin blended polyurethanes certainly enhance the

crystalline pattern of the synthesized bio-nanocomposites samples.

176


and elastomers (KPU10-KPU12)

177



The physical behavior of prepared polyurethane elastomers and bio-nanocomposites material

was evaluated by immersing the samples in water and in some appropriate solvent such as

DMSO for one week. After the cycle of 24 hours, the swelling level of chitin/curcumin/clay

based polyurethane elastomer and bio-nanocomposite was calculated and enlisted in table

4.15 and table 4.16 separately. From the results it was cleared that level of absorption showed

independent behavior over time but it depends upon the chain extenders chitin, curcumin and

clay. The results of table 4.15 showed that the synthesized samples displayed more

hydrophilicity than neat clay samples. When compare the effect of chitin/curcumin blended

PU and chitin/curcumin/clay blended PU, the result showed that clay based PU has more

water absorption character as compared to chitin/curcumin based PU. The blends form with

clay enhances the interaction of chitin/curcumin with PU backbone. Therefore, the absorption

properties of blended PU have been increased. A possible explanation for such an

improvement could be the creation of a three-dimensional network of interconnected long

silicate layers which enhance the surface area of synthesized samples which has ultimately

improved the absorption properties. The swelling behavior data of prepared polyurethane

samples is given in table 4.16. From the data, it is cleared that the swelling character of

polyurethane samples have been increased by using the clay in chitin, curcumin based PU

samples. In contrast to it the prepared polyurethane samples in which clay is not used have

less swelling behavior as compared to clay based polyurethane. The clay particles enhance

the intractability of PU prepolymer with chitin, curcumin which ultimately increase the

swelling characters of synthesized materials. The water absorption and swelling behaviors of

chitin, curcumin based polyurethane has been increased by using the clay. Finally, it may be

concluded that curcumin/chitin/clay blended polyurethane bio-nanocomposite possessed

dimensional physical properties as compared to curcumin/chitin blended PU and can be

suggested as a good biofunctional material.

178

Table 4.15: Water absorption of chitin/curcumin/clay based polyurethane samples


Sample

code

0 day

* 1

st day 2

nd day 3

rd day 4

th day 5

th day 6

th day 7

th day

KPU10 1.113 ±

0.07

1.125 ±

0.08

1.132 ±

0.04

1.138 ±

0.06

1.142 ±

0.04

1.145 ±

0.05

1.147 ±

0.07

1.148 ± 0.08

KPU10

-clay

1.113 ±

0.05

1.156 ±

0.07

1.173 ±

0.04

1.189 ±

0.02

1.203 ±

0.06

1.217 ±

0.05

1.229 ±

0.03

1.251 ± 0.02

KPU11 1.093 ±

0.06

1.104 ±

0.07

1.111 ±

0.09

1.116 ±

0.06

1.120 ±

0.08

1.123 ±

0.09

1.124 ±

0.07

1.125 ± 0.06

KPU11

-clay

1.093 ±

0.06

1.125 ±

0.05

1.132 ±

0.04

1.148 ±

0.03

1.162 ±

0.02

1.175 ±

0.04

1.187 ±

0.06

1.198 ± 0.03

KPU12 1.103 ±

0.05

1.114 ±

0.07

1.121 ±

0.08

1.126 ±

0.09

1.130 ±

0.04

1.137 ±

0.05

1.134 ±

0.07

1.134 ± 0.06

KPU12

-clay

1.103 ±

0.04

1.135 ±

0.05

1.142 ±

0.02

1.157 ±

0.03

1.162 ±

0.06

1.168 ±

0.04

1.166 ±

0.03

1.167 ± 0.02



179

Table 4.16: Swelling behavior of chitin/curcumin/clay based PU samples

Sample

number

Sample code Density

(g/cc)


degree of

swelling (1/vR) 0 day

* 1

st day 3

rd day 5

th day 7

th day

1 KPU10 1.048 1.121 1.521 1.601 1.631 1.611 1.631± 0.08

2 KPU10-clay 1.047 1.121 1.533 1.644 1.683 1.703 1.642 ± 0.10

3 KPU11 1.050 1.191 1.611 1.681 1.711 1.691 1.561 ± 0.11

4 KPU11-clay 1.049 1.191 1.632 1.693 1.772 1.743 1.570 ± 0.13

5 KPU12 1.052 1.221 1.641 1.701 1.691 1.681 1.521 ± 0.12

6 KPU12-clay 1.051 1.221 1.662 1.732 1.722 1.732 1.528 ± 0.15



180

Chapter 5

SUMMARY

Polyurethanes (PUs) and natural polymer blends are considered actively for introducing

novel biomaterials for different uses. PU combines isocyanate and hydroxyl groups to form a

urethane linkage. In this novel study PUs blends varying the diisocyanates structure (HMDI,

H12MDI, IPDI, TDI, MDI)/HTPB with equal mole ratio of curcumin/BDO have been

synthesized. Similarly, PUs including HTPB/clay/HMDI with various mole ratios of

curcumin/chitin/BDO was synthesized via step growth polymerization. In this way eight

series of polyurethanes were prepared, as in first four parts (series) polyurethane elastomers

were prepared while in last four parts (series) polyurethane bio-nanocomposites were

prepared (using HTPB / HMDI / chitin / curcumin / BDO / clay). Although in first part PU

elastomer is prepared by using equal mole ratio of curcumin/BDO and varying the

diisocyanates structure (HMDI, H12MDI, IPDI, TDI and MDI) and in other three parts (2,3

&4) are synthesized (using HTPB / HMDI / chitin / curcumin / BDO). Curcumin/chitin/BDO

were used in pristine form (with clay and without clay) and in the blend form (with clay and

without clay) for synthesis of various samples of polyurethane elastomers and bio-

nanocomposites. Characteristic techniques such as FTIR, SS1HNMR, SEM, XRD, TGA and

DSC were performed to evaluate the properties of pristine and blended PU elastomers and

bio-nanocomposites. The antimicrobial activity tests (anti-bacterial and anti-fungal ) for

different samples of the curcumin based polyurethane with varying diisocyanates structure

(only part-1) was studied in order to determine the diisocyante structure effects on the

biocompatibility of the prepared PU samples. Degree of absorption and swelling behaviors

was evaluated by treating with water and organic solvent.

The elastomers and bio-nanocomposites formation were confirmed by FTIR

technique. The appearance of N─H peak and disappearance of NCO peak confirmed the

completion of reaction, that is elastomers and composites have been formed. The presence of

characteristic primary and secondary amide, keto-enol and aromatic ring stretching peaks

confirmed the successful incorporation of chitin, CUR, BDO in PU elastomers and chitin,

curcumin, BDO, clay in PU bio-nanocomposites. In order to observe whether the vibrational

mode changes by the addition of clay in PU backbone, the FTIR spectrum of prepolymer with

and without clay were compared. It is obvious from figures 4.5(a) and 4.27(a) that both the

spectrum have no difference and showed a complete set of peaks at the same positions that is

clay did not create problem in prepolymer synthesis. From FTIR analysis it was evaluated

181

that chitin possessed tri-functional behavior which may help it to develop network structure,

the stable keto-enol structure of curcumin along with intermolecular hydrogen bonding

formed stable PU. With the help of FT-IR technique H-bonding between the hard segments

was observed.

The structural characterization of pristine and blends based chitin, curcumin, and

BDO based polyurethane elastomers were done using SS1HNMR technique. The structural

transition due to the change in hydrogen bonding was confirmed by using this technique.

Involvement of chitin, curcumin and BDO were confirmed by the appearance of two main

peaks in range 1.50-8.50 ppm of protons signals in SS1HNMR spectrum. All the

characterized samples of polymer showed the solid state 1HNMR peaks according to the

strength of protons present in structure of polymers, which confirmed the formation of final

polymer samples.

Surface morphology of PU elastomers and composites were studied by using SEM

technique indicated that the blend is rough and heterogeneous, further it confirmed the

interaction among the functional groups of the components. It also confirmed that chitin

based PU possessed crosslinking behavior as compared to curcumin and BDO based PUs.

SEM results revealed that by using clay in synthesized samples the homogeneity and

uniformity of surface particles is improved. It is obvious from the results of SEM images that

bentonite nanoclay are fully dispersed in all the studied samples and presence of the clay

contents is clearly visible on the surface of bio-nanocomposites samples.

The crystalline behavior of the synthesized polymer elastomers and bio-

nanocomposites were investigated by XRD technique and found that crystallinity increased

by increasing the mole ratio of chitin in elastomers as compared to curcumin and BDO, the

presence of chitin also favors the formation of more ordered structure. The 2θ values of

crystalline peaks of KPU3, KPU6, KPU5, KPU4, KPU2 and KPU1 are 21°, 18.5

°, 16.8

°,

15.8°, 17.5

° and 15.5

° respectively. In comparative study of elastomers and bio-

nanocomposites by XRD technique it was cleared that by using clay the ordered pattern is

increased and thus crystallinity bio-nanocomposites as compared to elastomers is increased.

The 2θ values of crystalline peaks of KPU1, KPU1/clay, KPU2, KPU2/clay, KPU3,

KPU3/clay are 15.5°, 16

°, 17.5

°, 18.2

°, 21

°, 22

° respectively.

It was found that aliphatic diisocyanate based PU showed substantially lower

antimicrobial activity as compared to the PU having aromatic diisocyanate. Future

investigation of blends will explore the antimicrobial and biological activities for

pharmaceutical/clinical applications.

182

Water immersion and equilibrium degree of swelling tests confirmed the hydrophobicity/

hydrophilicity and swelling behavior of elastomers and composites. From the results it is

cleared that chitin based elastomers possess poor hydrophilicity and swelling character as

compared to elastomers without chitin. To understand the effect of nano fillers on PU

absorption and swelling character, the results of samples with and without clay were noted. It

is revealed from the results that clay enhances the absorption and swelling behavior of PUs.

DSC analysis showed that chitin/curcumin based PU show better thermal stability and

crystallinity but by using clay in the mentioned sample this behavior became more

pronounced. Thermogravimetric analysis (TGA) of PU blends indicated a better thermal

stability with 1M:0.5M:0.5M of chitin, curcumin and BDO respectively. Also the TGA

properties of synthesized samples were improved by using clay. The temperature value at

which 20% weight loss occurred of KPU10, KPU10-clay, KPU11, KPU11-clay, KPU12 and

KPU12-clay are 368 ºC, 382

ºC, 374

ºC, 395

ºC, 388

ºC and 410

ºC respectively. These results

confirmed that nanofiller improved the thermal properties of synthesized samples. From the

above results it was concluded that the blends of curcumin/chitin/BDO based polyurethane

samples retain good physical, surface and thermal properties as compared to pristine BDO,

curcumin based polyurethane. Secondly, by using the clay in above mentioned samples the

physical, surface and thermal properties are enhanced as compared to samples without using

clay. Study of structure‒property relationship for synthesized polyurethane elastomers and

nanocomposites showed that the main determining factors for detected properties were the

structural and thermal of curcumin/chitin/BDO/clay in the PU backbone.

183

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APPENDICES

Published Articles

1- Kashif Mahmood, Khalid Mahmood Zia,Waseem Aftab, Mohammad Zuber, Shazia

Tabasum, Aqdas Noreen & Fatima Zia (2018). Synthesis and characterization of

chitin/curcumin blended polyurethane elastomers. International Journal of Biological

Macromolecules, 113 150–158.

2- Kashif Mahmood, Khalid Mahmood Zia, Mohammad Zuber, Shazia Tabasum, Saima

Rehman, Fatima Zia & Aqdas Noreen (2017). Morphological and thermal studies of

chitin-curcumin blends derived polyurethanes. International Journal of Biological

Macromolecules, 105 1180–1191.

3- Kashif Mahmood, Iqra Noreen, Muhammad Riaz, Mohammad Zuber, Mahwish

Salman, Saima Rehman & Khalid Mahmood Zia (2016). Synthesis and

characterization of novel curcumin based polyurethanes varying diisocyanates

structure. Journal of Polymer Research, 23, 233.

4- Kashif Mahmood, Khalid Mahmood Zia, Mohammad Zuber, Zill-i-Huma Nazli,

Saima Rehman & Fatima Zia (2016). Enhancement of bioactivity and bioavailability

of curcumin with chitosan based materials. Korean Journal of Chemical Engineering,

33(12), 3316-3329.

5- Kashif Mahmood, Khalid Mahmood Zia, Mohammad Zuber, Mahwish Salman &

Muhammad Naveed Anjum (2015). Recent developments in curcumin and curcumin

based polymeric materials for biomedical applications: A review. International

Journal of Biological Macromolecules, 81, 877–890.

6- Khalid Mahmood Zia, Kashif Mahmood, Mohammad Zuber, Tahir Jamil &

Muhammad Shafiq (2013). Chitin based polyurethanes using hydroxyl terminated

polybutadiene. Part I: Molecular engineering. International Journal of Biological

Macromolecules, 59, 320– 327.

7- Khalid Mahmood Zia, Naureen Aziz Qureshi, Mohammad Mujahid, Kashif Mahmood

& Mohammad Zuber (2013). Chitin based polyurethanes using hydroxyl terminated

polybutadiene, Part II: Morphological studies. International Journal of Biological


8- Khalid Mahmood Zia, Mohammad Zuber, Muhammad Jawwad Saif, Mohammad

Jawaid, Kashif Mahmood, Muhammad Shahid, Muhammad Naveed Anjum & Mirza

Nadeem Ahmad (2013). Chitin based polyurethanes using hydroxyl terminated

203

polybutadiene,part III: Surface characteristics. International Journal of Biological

Macromolecules, 62, 670– 676.

synthesis and characterization of biofunctionalized

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