sol–gel synthesis of 3-(triethoxysilyl)propylsuccinicanhydride containing fluorinated silane for...

ORIGINAL PAPER

Sol–gel synthesis of 3-(triethoxysilyl)propylsuccinicanhydridecontaining fluorinated silane for hydrophobic surface applications

Nadir Kiraz • Esin Burunkaya • Omer Kesmez •

Meltem Asilturk • H. Erdem Camurlu •

Ertugrul Arpac

Received: 9 April 2010 / Accepted: 13 July 2010 / Published online: 21 July 2010

� Springer Science+Business Media, LLC 2010

Abstract In this paper, novel fluorinated silane compound

was prepared by adding hydroxyl terminated Fluoro-

link D10H oligomer to 3-(triethoxysilyl)propylsuccinican-

hydride. The obtained silane system was independently

composed with 3-Aminopropyltrimethoxysilane, 3-Glyci-

dyloxypropyltrimethoxysilane and 3-Glycidyloxypropyl-

triethoxysilane and, then the prepared coating solutions

were applied to glass surface by spin-coating method. The

chemical bonding between groups in system was investi-

gated by Fourier Transform Infrared Spectroscopy analyses.

The elemental composition of coatings was determined

using Energy Dispersive X-ray Spectroscopy analyses. Its

structure and surface properties were analyzed by scanning

electron microscopy, atomic force microscopy, contact

angle measurement and Ultraviolet–visible Absorption

Spectroscopy. The amounts of fluorine on the coatings

prepared with GF20-D10H-AMMO, GF20-D10H-GLYEO

and GF20-D10H-GLYMO are 31, 32 and 34% at, respec-

tively. Transparent coatings with smooth surface and

uniform thickness were observed. The coatings had nano-

scale roughness. The contact angles of coatings for water

ranged from 88 to 107o, and that of n-hexadecane ranged

from 53 to 60o.

Keywords Fluorinated silane � Sol–gel �Hydrophobicity � Oleophobicity � Transparent coatings

1 Introduction

In recent years, various functional coatings have been

developed instead of bulk materials. Utilizing these func-

tional coatings, various additional functions, such as:

hydrophobic, hydrophilic, antibacterial or photocatalytic,

etc., can be gained to the substrate material. Silanes are the

most common compounds used in functional surface

coatings. They form a siloxane network by hydrolysis of

the alkoxysilanes tightly bound to the material surface in

which silane coupling agents react with surface hydroxyl

[1]. If an organic group with a certain function is intro-

duced in silane coupling agent molecules, the function of

the group can be fixed on the material surface. For exam-

ple, when a fluoroalkyl group is introduced, the surface

becomes water and oil repellent [2–11, 15–19]. Fluorinated

compounds are those unique compounds which possess

many excellent properties including high lubricativity,

noncombustibility, and chemical inactivity, in addition to

water repellency and oil repellency. Consequently, fluori-

nated compounds have been used as highly functional and

performable materials because of its superb characteristics.

When fluorinated compounds are applied to any surface,

fluoromethyl (-CF3) groups are uniformly arranged on

surface and the surface energy is effectively reduced to as

low as 8 mJ/m2 [12, 13]. Only a very small quantity of

N. Kiraz � E. Burunkaya � O. Kesmez � E. Arpac

Department of Chemistry, Akdeniz University, 07102 Antalya,

Turkey

M. Asilturk (&)

Prof.Dr.Hikmet Sayılkan Research and Development Laboratory

for Advanced Materials, _Inonu University, 44280 Malatya,

Turkey

e-mail: [email protected]

H. Erdem Camurlu

Department of Mechanical Engineering, Akdeniz University,

07058 Antalya, Turkey

N. Kiraz � E. Burunkaya � O. Kesmez � E. Arpac

NANOen R&D Ltd, Antalya Technopolis, Akdeniz University

Campus, 07102 Antalya, Turkey

123

J Sol-Gel Sci Technol (2010) 56:157–166

DOI 10.1007/s10971-010-2289-3

fluorinated compound is need to obtain hydrophobic sur-

face. The fluorinated compounds have the tendency to

migrate towards the air/film interface and minimize the

interfacial energy [14]. Because, the driving force for

surface segregation of the fluorine is the difference

between surface energies of the groups with fluorine and

the groups without fluorine.

Fluoroalkylsilanes (FAS), such as: heptadecafluorodecyl-

triclorosilane, perfluoro-octyltriclorosilane, heptadecafluoro-

decyltrimethoxysilane, perfluorododecyltrimethoxysilane.

are the most important fluorinated compounds used in

hydrophobic surface researches [7–11]. The surfaces applied

to fluoroalkylsilane have some advantages, such as: flexibil-

ity, heat resistant, stability due to the unique molecular

structure of silicone and fluorine groups in structure. How-

ever, the using of fluoroalkylsilanes is limited in industrial

applications due to high cost. Fluorinated silanes are alter-

native compounds to fluoroalkylsilanes and they are widely

used for hydrophobic surface applications [15–19]. In this

study, we synthesized fluorinated silane compound and

demonstrated that the glass surfaces can be coated with this

compound. We found that contact angles of water and hexane

on the coated surfaces were higher than those on the uncoated

surface.

The aim of this study was to prepare novel fluorinated

silane system that had good properties, such as: lower

prices, stronger water and oil repellency. For this purpose,

we used 3-(triethoxysilyl)propylsuccinicanhydride as link-

ing silane compound and hydroxyl terminated Fluorolink

D10H oligomer as fluorine source. Fluorolink D10H is a

commercial oligomer which has OH functional group and

contains CF3 and CF2 groups. Weight of fluorine in Flu-

orolink D10H is 61%. We investigated applicability of new

fluorinated silane compound with three different silane

compounds for hydrophobic surface applications.

2 Experimental section

2.1 Chemicals

3-(triethoxysilyl)propylsuccinicanhydride (commercial

name: GF20, 94%, ABCR) as linking silane compound,

hydroxyl terminated oligomer (commercial name: Fluoro-

link D10H, Solvay Solexis) as fluorine source, and Alu-

minium chloride (AlCl3, % 99.9, Aldrich) as catalyst were

used to prepare fluorinated silane compounds. 3-Glycidy-

loxypropyltrimethoxy-silane (GLYMO, Degussa), 3-Gly-

cidyloxypropyltri-ethoxysilane (GLYEO, Degussa) and

3-Aminopropyltrimethoxysilane (AMMO, % 97, Aldrich),

2-isopropoxyethanol (IPE, 99%, Aldrich), 2-butoxyethanol

(BG, 99%, Alfa Aesar), 0.1 M nitric acid (HNO3, 65%,

Merck) and deionized water were used to prepare the coating

solutions. The contact angles of films were measured against

water and n-hexadecane (Merck).

2.2 Fluorination of 3-(triethoxysilyl)propyl-

succinicanhydride

Fluorinated silane compound was prepared as in the fol-

lowing steps: 4.534 g GF20 and 9.905 g Fluorolink D10H

were stirred at room temperature. The mol ratio between

GF20 and D10H was 1. After 0.005 g AlCl3 (AlCl3/

GF20 = 0.001) directly was added to this mixture. Then,

they were stirred during 24 h at room temperature. The

prepared fluorinated silane compound was fluid, homoge-

neous and colorless. It was used as is in the coating

solutions.

2.3 Preparation of coating solutions

Three different silane systems were used in this study. The

first chemical system consisted of fluorinated GF20 com-

pound (GF20-D10H) and AMMO. The coating solution

containing this chemical system was prepared by mixing

GF20-D10H, AMMO, and 2-isopropoxyethanol and reac-

ted with water and acidic conditions at room temperature.

The mixture of GF20-D10H and AMMO was prepared and

then diluted with alcohol at room temperature under stir-

ring for 1 h. To hydrolyze of alkoxide groups, 0.1 M nitric

acid solution immediately was added to the solution. All

coating solutions were prepared with molar ratio of GF20-

D10H:AMMO (GLYEO and GLYMO) equal to 1:1.

The second and third chemical systems consisted of

GF20-D10H-GLYEO and GF20-D10H-GLYMO, respec-

tively. The coating solutions of these systems were pre-

pared with the same procedure which described above. The

compositions of all coating solutions used in this study are

summarized in Table 1. As it can be seen in Table 1, the

weight percentages of chemical systems in coating solu-

tions are 10 and 20.

2.4 Coated of glass surface

Before the coating process, for abrading and cleaning,

surface of glass substrates (plate, 10 cm W 9 10 cm

L 9 0.3 cm T) was polished with CeO2 (Technical grade,

Calıskanlar Chem., Turkey) and rinsed with water. After

this process, they treated with 30% (w/w) aqueous NaOH

solution in an ultrasonic bath at 80 �C for 30 min, and then

they were again cleaned with distilled water and placed in

aqueous HNO3 (10%, w/w) solution. For neutralization of

surfaces, they were held in this acidic medium about

30 min. The substrates were cleaned with distilled water

and placed in aqueous HNO3 (10%, w/w) solution and

finally held in this medium about 10 min for neutralization.

158 J Sol-Gel Sci Technol (2010) 56:157–166

123

The substrates were washed again with distilled water with

rubbing until pH of the wash water was neutral as con-

trolled by measuring the pH, kept at 110 �C for 2 h in

drying oven, and then cooled to room temperature.

The cleaned glass surface was coated by spin coating

method at 500, 750, 1,000 and 1,250 rpm for 10 s with the

different coating solutions. The coated glasses were firstly

delayed for 1 h at room temperature, and then they were

heated to 170 �C and cured for 2 h at this temperature in an

oven.

2.5 Characterization

Fourier transform infrared spectrophotometer (ATR-FTIR;

Varian 1,000 model) was used to attend the formed

chemical bonds between GF20 with D10H and the other

silane compounds which used coating solution.

Glass surfaces were coated with coating solution using

hand made spin coater. The curing of coatings samples was

made by (Thermo Electron Corporation, Heraeus model)

oven.

The elemental composition of films on glass surface was

investigated by electron dispersive analyses of X-rays

(EDX). The optical properties of films were measured using

a Varian Carry 5,000 model UV–Vis–NIR spectrophotom-

eter combined with DRA apparatus. The microstructure of

films was observed by scanning electron microscopy (SEM,

Leo Evo 40 model). The surface morphology of films was

examined using atomic force microscopy (AFM) (PSIA Inc.,

XE-100E). Root-mean-square (rms) surface roughness was

evaluated from the AFM line profile data by XEI software.

Film thicknesses were determined by Filmetrics F20-HC

thin film measurement system. Static contact angles of films

were measured by NRL C.A. Goniometer (RAME-HART,

Inc. Model no.100-00). Water or hexadecane droplets were

placed onto surfaces using a microsyringe and contact angle

of the droplets was read by goniometer. Average of the

contact angles obtained from three different drops was used,

and difference of the three contact angels was within 1�.

3 Result and discussion

3.1 Reaction mechanism

GF20 is a silane compound which has three ethoxy groups and

one succinic anhydride ring. Fluorination reaction of GF20 is

a chemical bonding occurring between succinic anhydride

rings and hydroxyl group of D10H. In Scheme 1, the sche-

matic reaction mechanism of GF20-D10H, GF20-D10H-

AMMO, GF20-D10H-GLYMO and GF20-D10H-GLYEO

systems was presented. As shown in step 1, succinic anhy-

dride ring of GF20 was opened by the attack of unsaturated

electrons above oxygen atom of D10H to the carbon atom of

the carbonyl group of the succinic anhydride ring. AlCl3 as

catalyst was used to provide this reaction. Thus, fluorinated

silane compound (GF20-D10H) which had terminal carbox-

ylic acid group was acquired by sol–gel reaction.

Step II indicated the reactions between GF20-D10H with

the other silane compound. Here, the epoxy modified alk-

oxysilanes (GLMYO and GLYEO) and the amine modified

alkoxysilanes (AMMO) were used to form organic–inor-

ganic polymer network in coatings. As shown in step II-A,

reactions of GF20-D10H with GLYMO or GLYEO, which

is an epoxy ring opening reaction, occur between carboxylic

acid group of GF20-D10H with epoxy ring of GLYMO or

GLYEO. In GF20-D10H-AMMO system, the peptide bond

forms due to the reaction between amine groups of AMMO

with carboxylic acid group of GF20-D10H which was

indicated in step II-B. 0.1 M HNO3 was used for hydrolysis

and polycondensation reaction alkoxide groups of silanes in

all systems. As shown in step III-A and III-B, the polymeric

network was ensured by further condensation reactions. As a

final step, terminal F groups containing organic and inor-

ganic polymeric network was transferred to glass surface.

Table 1 Compositions of coating solutions

Coating solution: GF20-D10H-AMMO GF20-D10H-GLYEO GF20-D10H-GLYMO

Weight ratio: 10 wt% 20 wt% 10 wt% 20 wt% 10 wt% 20 wt%

Amount (g)

GF20-D10H 1.500 2.117 1.500 1.855 1.500 1.786

AMMO 0.267 0.378 – – – –

GLYEO – – 0.415 0.513 – –

GLYMO – – – – 0.352 0.420

IPE 17.352 10.892 18.684 10.270 18.117 9.592

0.1 M HNO3 0.161 0.228 0.161 0.199 0.161 0.192

J Sol-Gel Sci Technol (2010) 56:157–166 159

123

H5C2O

H5C2O

OC2H5

Si

(CH2)3

O

O

O

C

C

CH

CH2

OH

F3C

(CF2)10

(CH2)8

.. ..

H5C2O

H5C2O

OC2H5

Si

(CH2)3

O

O

OH

C

C

CH

CH2O

CF3

(CF2)10

(CH2)8

(CH2)3

CH2CH2

CH

O

O

OR

OR

OR Si NH2

(H2C)3

H5C2O OC2H5

OC2H5Si

Si

SiSi

Si

Si

Si

O

OO

OO

O

Si (CH2)3

O

O

C

C

CH

CH2

O

CF3(CF2)10

(CH2)8

NH

(CH2)3

Si

O

Si Si

Si O

OO

Si

Si

Si

O

O

O

Si

(CH2)3

O

O

C

C

CH

CH2O

CF3

(F2C)10(CH2)8

(H2C)3 CH2CH2

CH-O

O

Si

O

O

Si

Si

Si

O

O

O

Si

Si

O

O

Si

(CH2)3

O

O-

C

C

CH

CH2

O

CF3

(F2C)10 (CH2)8

(CH2)3

CH2

CH2

CH

O-

O

Si

O

Si

Si

Si

O

O

O

Si

Si

O

O

Si

(CH2)3

O

O-

C

C

CH

CH2

O

F3C

(CF2)10(H2C)8

(CH2)3

CH2

CH2

CH-O

O

Si

SiSi

Si

Si

Si

O

OO

O

O

O

Si (CH2)3

O

O

C

C

CH

CH2

O

F3C

(CF2)10

(H2C)8

NH

(CH2)3

Si

SiSi

Si

Si

Si

O

OO

O

O

Si(CH2)3

O

O

C

C

CH

CH2

O

CF3

(F2C)10

(CH2)8

NH

(CH2)3

Si

D10 H

GF20

GLYMO or GLYEO

AMEO

Step I

Step II

-A Step II -B

Step III-AStep III-B

AlCl3

0.1 M HNO3

..........

.

O

.

SiO

O

.

O

SiO

O

.

OO

.O

O

.

O

.

O

O.

O

Si

O

.

O

.

Si Si Si Si Si

O

.

SiO

.

O

Si

.

F

F

FC

.

F

F

FC

.

F

F

FC

.

F

F

FC

.

F

F

FC

.

F

F

FC

.

F

F

FC

Glass

Scheme 1 Schematic representation of reaction mechanism


123

3.2 FT-IR studies

The chemical reaction between GF20 with D10H which

proved formation of novel silane compound was investi-

gated by FT-IR analysis. The FTIR spectrum of GF20 and

D10H show the characteristic carbonyl stretching at

1,760–1,820 cm-1 and O–H stretching mode around

3,200–3,450 cm-1, respectively. As shown in Fig. 1a, after

the chemical reaction occurred between carbonyl group of

anhydride and the hydroxyl group of D10H, the broad band

at 1,760–1,820 cm-1 disappeared completely in the GF20-

D10H and the C–O stretching band was formed at

1,728 cm-1. This chemical reaction was designated as

esterification. The symmetric and asymmetric C–O–C

vibrations, which belonged to formed ester, were not shown

at 1,050–1,160 cm-1 due to overlapping with symmetric

and asymmetric Si–OR vibration appearing in the same

region. In novel compounds, C–F and fluorine substituted

C–H vibration were also shown at 1,357 cm-1 and

3,039 cm-1, respectively. According to FTIR dates, the

novel fluorinated silane compound was formed.

The other aim of this study was to form hydrophobic coating

systems by using this fluorinated silane compound. For this

purpose, combinations of fluorinated silane compounds with 3-

Aminopropyltrimethoxysilane, 3-Glycidyloxypropyltriethox-

ysilane, and 3-Glycidyl-oxypropyltrimethoxysilane were used.

As shown in Fig. 1b, after the chemical bonding was even-

tuated out of reaction between carboxylic acid group of

GF20-D10H with amino group of AMMO, the carbonyl

bands at 1,735 cm-1 disappeared in the GF20-D10H-

AMMO and N–H deformation vibration around 1,550 cm-1

formed. The bonding reactions of epoxy modified silane

(GLYEO and GLYMO) with fluorinated silane compound

also were eventuated out of epoxy ring opening reaction.

The peaks related to epoxy ring considered at 1,280 cm-1

and 948 cm-1 in Fig. 1c, d. A comparison of spectrum

AMMO and GF20-D10H-AMMO indicated that after

reaction these peaks were completely disappeared.

All FTIR spectra (Fig. 1a–d) were shown similar bands

between 2,800–3,000 cm-1 and 700–1,220 cm-1. The

bands at 2,800–3,000 cm-1 were originated from several

C–H stretching of the silane backbones and alkyl groups.

The symmetric and asymmetric Si–O–R stretching bands

were shown between the ranges from 1,050 to 1,220 cm-1 in

spectrums. The Si–O vibrations were considered around 700

and 900 cm-1.

3.3 Surface morphological studies

The SEM micrographs of films prepared from coating

solution containing 10 wt% GF20-D10H-AMMO, GF20-

D10H-GLYEO and GF20-D10H-GLYMO were shown in

Fig. 2a–c, respectively. All films were treated for 2 h at

40080012001600200024002800320036004000

Wavenumber (cm-1

)

Tra

nsm

ittan

ce (

a.u)

D10H

GF20

GF20-D10H

C-O

anhyride ringC=O and C-H

Si-OC2H5 and C-O-C

C-F

C-O-C

Si-OC2H5

C-OC-F

(a)

40080012001600200024002800320036004000

Wavenumber (cm-1)

Tra

nsm

ittan

ce (

a.u.

)

GF20-D10H-AMMO

AMMO

GF20-D10H

1735 cm-1

1550 cm-1

(b)

40080012001600200024002800320036004000

Wavenumber (cm-1)

Tra

nsm

ittan

ce (

a.u.

)

GF20-D10H

GLYEO

GF20-D10H-GLYEO

1735 cm-1

948 cm-1

1280 cm-1

(c)

(d)

40080012001600200024002800320036004000Wavenumber (nm)

Tra

nsm

ittan

ce (

a.u.

)

GF20-D10H

GLYMO

GF20-D10H-GLYMO

1735 cm-1

1280 cm-1

Fig. 1 FTIR spectrums for GF20-D10H (a), GF20-D10H-AMMO

(b), GF20-D10H-GLYEO (c) and GF20-D10H-GLYMO (d)


123

170 �C. The film’s surfaces had a lot of dots like bubbles

suggesting that they occurred by quick evaporation of

solvent on the surface of films during heat treatment. The

dots were uniformly distributed on surface. The size of the

dots ranged from 500 nm to 1 lm according to composi-

tion of films. The thicknesses of films prepared from

GF20-D10H-AMMO, GF20-D10H-GLYEO and GF20-

D10H-GLYMO systems which can be shown in Fig. 2 are

160, 82 and 87 nm, respectively. The thickness of film

prepared from GF20-D10H-AMMO system was higher

than the other film. It was coated at 500 rpm by spin-

coating method while the others were coated at 1,250 and

1,000 rpm, respectively.

Figure 3a–c show the EDX spectra taken from four

regions on film’s surface prepared on glass substrate with

GF20-D10H-AMMO,GF20-D10H-GLYEO and GF20-

D10H-GLYMO which cured at 170 �C for 2 h, respectively.

In the spectra, some elements such as Na, Mg and Ca which

come from structure of glass in addition to mean element

such as Si, C, O and fluorine. The Si, C, O and fluorine

contents of all films are listed in Table 2. The fluorine

content percentages of GF20-D10H-AMMO, GF20-D10H-

GLYEO and GF20-D10H-GLYMO are around 31, 32 and

34 wt%, respectively. In the three systems, theoretical

fluorine content percentages are consistent with experi-

mentally determined fluorine content percentages.

AFM micrographs have been widely used to investigate

the surface morphology of hydrophobic films because it

could provide the direct information of the roughness of

surface. Roughness profile of films which were prepared

from dispersions containing 10 wt% GF20-D10H-AMMO,

GF20-D10H-GLYEO and GF20-D10H-GLYMO are shown

Fig. 4a–c, respectively. The average surface roughness was

calculated by the XEI software-2,006 (Version 1.6.1 alpha)

calculating the microstructure variables by the following

equation [20]:

Rsurf ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

X

Zið Þ2=Nq

ð1Þ

where Rsurf is the average surface roughness, Zi is the

current Z (height) value and N is the number of sample

points within the given area.

The roughness parameter of films showed that the

average roughness of GF20-D10H-AMMO film (Ra =

9.236 nm) was lower than that of GF20-D10H-GLYEO

(Ra = 67.755 nm) and GF20-D10H-GLYMO (Ra = 32.129

nm) films. This indicated that surface the film for GF20-

D10H-AMMO was considerably smooth.

The surfaces of the films for GF20-D10H-GLYEO and

GF20-D10H-GLYMO have many dispersed islands that

are distributed on the film surface. In the case of the GF20-

D10H-GLYEO coating, majority of the growing island are

protruded in the upward direction. The height and number

of the islands is increased in GF20-D10H-GLYEO film as

compared with GF-D10H-GLYMO film. The variation in

roughness for GF20-D10H-GLYMO film is obviously

shown in Fig. 4b.

SEM micrographs together with AFM images concluded

that dots-like pins or rods resulted from shrinkage or

Fig. 2 SEM images of the coatings on glass surface: a GF20-D10H-

AMMO, b GF20-D10H-GLYEO, c GF20-D10H-GLYMO coating


123

shrivelling as a result of rapid evaporation of the solvent on

the glass surface, which caused a nanoporous surface.

3.4 Contact angles studies

Contact angle of a liquid on a film surface is a direct

reflection of the hydrophilicity/hydrophobicity of the sur-

face [14]. In this study, water and n-hexadecane were

chosen as probe liquids. Table 3 shows contact angles of

water and hexadecane on films from GF20-D10H-AMMO,

GF20-D10H-GLYMO and GF20-D10H-GLYEO, respec-

tively. For the films which contained 10 wt% GF20-D10H-

AMMO, the water contact angles were changed from 86 to

90�. When the added GF20-D10H-AMMO content in the

films increased up, the water contact angles were decreased

from 6 to 13�. The n-hexadecane angles of films for

Fig. 3 EDX spectra

of GF20-D10H-AMMO (a),

GF20-D10H-GLYEO (b)

and GF20-D10H-GLYMO

coatings (c)


123

GF20-D10H-AMMO were contrary changed with the

water contact angles.

As given in Table 3, the water and n-hexadecane contact

angles of the films prepared from GF20-D10H-GLYEO

and GF20-D10H-GLYMO systems are higher than GF20-

D10H-AMMO systems. This difference is mainly related

to surface roughness because the roughness of films pre-

pared from GF20-D10H-GLYEO and GF20-D10H-GLY-

MO systems are higher than GF20-D10H-AMMO systems.

The hydrophobicity was decreased while the oleophobicity

was increased for films prepared from GF20-D10H-

GLYEO and GF20-D10H-GLYMO systems. This change

is related to the amount of compound in coating solution.

As expected, when the amount of compound increased

from 10 to 20 wt% in coating solution, the contact angles

of water and n-hexadecane were changed on all film sur-

face. The water contact angles of GF20-D10H-GLYEO

films were decreased range from 12 to 18� while the water

contact angles of GF20-D10H-GLYMO films also were

decreased range from 6 to 10�. This decreasing can also be

related to the surface roughness. The viscosity of 20 wt%

coating solution is higher than 10 wt% coating solution.

The evaporation of solvent would become very slow when

the viscosity of coating solution is high. The surface of film

prepared on glass substrate with this coating solution does

not have pores and cracks. Therefore, the water contact

angles of films were decreased due to decreasing of surface

roughness. Contact angles obtained by using the coatings

with fluoroalkylsilanes are between 100 and 110� [21]. The

contact angles obtained with the new silane coatings are

comparable with the literature (Table 4). Except for only

the fluorinated polyisociyanates [20], all of the fluorinated

silanes give rise to similar contact angles.

The hexadecane contact angles of films are proportional

to fluorine content in coating solution. When the amount of

compound increased from 10 to 20 wt% in coating solu-

tion, the contact angles of n-hexadecane were increased for

all film due to increasing fluorine content.

The effects of film thickness on the film wettability were

also investigated in this study. Normally, the film thickness

Table 2 The elemental contents of films which consisted of GF20-

D10H-AMMO, GF20-D10H-GLYEO and GF20-D10H-GLYMO

Atomic content (at.%)

Samples Si C O F F/Si

GF20-D10H-AMMO 13.72 13.95 41.29 31.05 2.26

GF20-D10H-GLYEO 12.29 13.87 41.77 32.07 2.61

GF20-D10H-GLYMO 13.68 16.91 35.40 34.01 2.49

Fig. 4 AFM images of GF20-D10H-AMMO (a), GF20-D10H-

GLYEO (b) and GF20-D10H-GLYMO (c) coatings


123

decreases when the spin rate of spin coater increases.

Table 3 also shows that both water and n-hexadecane

contact angles change when the spin rate increased from

500 to 1,250 rpm. Variation of contact angles of water

and n-hexadecane as a function of spin rate for the films

prepared from 10 wt% coating solutions (Table 3 1a, 2a

and 3a) is higher than those prepared from 20 wt%

coating solution. There is a decrease on the films prepared

from 10 wt% GF20-D10H-AMMO coating solutions and

at high spin rates. Since the data was determined within

±1� deviation, it was suggested that the variation is

related to the structure of the film surface. At high spin

rates, thinner and nonporous films are obtained. Since

surface energy of the nonporous surfaces are low, contact

angle is also low. As it can be seen in Table 3, the dif-

ference between the contact angles of the other films was

small or negligible.

3.5 Optical transmission studies

Figure 5a–c show the optical transmission spectra of the

films which prepared from dispersions containing 10 wt%

GF20-D10H-AMMO, GF20-D10H-GLYEO and GF20-

D10H-GLYMO systems, respectively. After the surfaces of

glass coated with investigated systems, no decreasing was

shown in transmittance of glass in the visible wavelength

range. The films had excellent optical transmittance at

range 350 from 800 nm. The uncoated glass showed 90%

transmission at 550 nm; whereas the all films showed about

92% transmission in this wavelength. The optical band gap

energy (Eg) was estimated by the method proposed by

Wood and Tauc [20]. According to these authors the

optical band gap is associated with absorbance and photon

energy by the following equation:

hma / hm� Eg

� �2 ð2Þ

where a is the absorbance, h is the Planck constant, m is the

frequency and Eg is the optical band gap energy. The plot

of the absorbance vs. photon energy, of the films prepared

at different spin rate. The extrapolation of the straight lines

to a = 0 gives the values of optical band gap. It is found

that the optical direct transitions lie in the range

3.84 ± 0.01 eV for the films.

The small Eg values can be related to the presence of

intermediary energy levels within the band gap of disor-

dered thin films. These energy levels are dependent of the

degree of structural order–disorder in the lattice. Therefore,

the increase of structural organization in the thin films

leads to a reduction of these intermediary energy levels and

consequently increases the Eg values [20]. In this study,

high Eg values show that the films on glass substrate have

good structural organization and low defect concentration.

There is no considerable change on the optical transmit-

tance of the films as a function of the film thickness which

decreases with increasing spin rate.

Table 3 Contact angles of the films for water and n-hexadecane

Coating system Spin rate (rpm)

500 750 1,000 1,250 500 750 1,000 1,250

Water contact angle (�) (±1) n-Hexadecane contact angle (�) (±1)

1a 103 97 97 94 44 47 48 46

1b 90 90 86 88 59 60 61 59

2a 90 91 94 89 53 54 53 54

2b 107 106 106 106 59 57 60 58

3a 100 96 97 98 53 49 51 54

3b 107 106 107 104 60 60 60 62

1a: GF20-D10H-AMMO, 2a: GF20-D10H-GLYEO and 3a: GF20-D10H-GLYMO (10 wt.% in IPE)

1b: GF20-D10H-AMMO, 2b: GF20-D10H-GLYEO, 3b: GF20-D10H-GLYMO (20 wt% in IPE)

Table 4 Comparison of contact angle of water on the film prepared

using various fluorinated compounds

Fluorinated compound hWater

(�)

Reference

CF3(CF2)7CH2CH2Si(OCH3)3 110 [7]

CF3(CF2)5CH2CH2Si(OC2H5)3 104 [8]

C8F17SO2NHC3H6Si (OCH3)3 100–105 [9]

CF3(CF2)5CH2CH2Si(OC2H5)3 100 [10]

CF3(CF2)9(CH2)2Si(OCH3)3 110-112 [11]

CF3(CF2)7C2H4(Si(OCH3)3 112 [12]

Poly[3,3,4,4,5,5,6,6,6-nonafluorohexyl-

methylsiloxane]

110–111 [13]

Fluorinated polyisocyanates (C6F13CH2CH2OH

and C8F17CH2CH2OH ? HDI) (HDI:

hexamethylene diisocyanate and an HDI

trimer)

120 [20]

GF20-D10H-GLYMO 107 In this

studyGF20-D10H-GLYEO 106


123

4 Conclusions

A novel fluorinated silane compound consisting GF20

(3-(triethoxysilyl)propyl-succinicanhydride) and Fluorolink

D10H was synthesized by sol–gel process. To investigate

employability of the new silane at hydrophobic surface

applications, inorganic–organic hybrid systems were pre-

pared by mixing the fluorinated silane with 3-Aminopro-

pyltrimethoxysilane (AMMO), 3-Glycidyloxypropyltri-

methoxysilane (GLYMO) or 3-Glycidyloxypropyltriethox-

ysilane (GLYEO). The films on the glass surface are highly

transparent and they have uniform thicknesses and nano-

scale roughness. The water and hexadecane contact angles

of films are between 88–107� and 53–60�, respectively. The

films of GF20-D10H-GLYEO system showed the best

hydrophobicity, whereas hydrophobicity of the films of

GF20-D10H-AMMO system is low. The study showed that

the new fluorinated silane can be used both in the hydro-

phobic and oleophobic applications. It can be used by

combination with different silanes or nanopowders for

enhancing the contact angles. It can be an alternative to the

commercially available fluorinated silanes because this

material is cheap compared to fluoroalkylsilanes.

Acknowledgment Authors would like to thank Akdeniz University

Research Fund for financial support. Technical and financial support

of NANOen Ar-Ge Ltd.Sti. is gratefully acknowledged.

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21. Takahashi O, Arai H, US patent 5250322, Central Glass Co

0

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200 300 400 500 600 700 800

Fig. 5 UV-vis spectra of GF20-D10H-AMMO (a), GF20-D10H-

GLYEO (b) and GF20-D10H-GLYMO (c) coatings


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sol–gel synthesis of 3-(triethoxysilyl)propylsuccinicanhydride containing fluorinated silane for...

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