S1

Supporting information

for

Performances of Chitosan Grafted onto Surface

of Polyacrylonitrile Functionalized

through Amination Reactions

Vasilica Popescu a*

, Emil Ioan Muresan b

a, * “Gheorghe Asachi” Technical University, Faculty of Textiles, Leather Engineering and

Industrial Management, 29 Blvd. Mangeron, TEX 1 Building, Iasi-700050, Romania;

vpopescu65@yahoo.com

b “Gheorghe Asachi” Technical University, Faculty of Chemical Engineering and Environment

Management, 73 Blvd. Mangeron, Iasi 700050, Romania; eimuresan@yahoo.co.uk

Corresponding author: vpopescu65@yahoo.com; tel.: +40 (0)726371108

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S1. Characterization of Dyestuffs and Polymers (PAN and CS)

S2. FTIR Analysis

S2.1.Spectral Subtraction Method

S2.2.Frequencies Characteristic of Untreated PAN Fiber

S2.3.Results of Spectral Subtraction for Grafted Samples

S3. SEM Analysis

S4. Nitrogen (N) Content

S5. Yellowness Index and Color Measurements

S6. Tensile strength

S7. Fastness properties

S3

S1. Characterization of Dyestuffs and Polymers (PAN and CS)

Table S1. Chemical stucture of dyestuffs

Chemical structure Abbreviation Acid group no.

Molecular weight [g]

C.I. Acid Red 88

AR 88

1

400.38

C.I. Acid Violet 48

AV 48

2

764.81

The physical-chemical characterization of polymers (PAN and CS)

1) PAN fibers are ternary copolymers: 85% acrylonitrile (AN) + 10% vinyl acetate (AV) + 5%

α methyl styrene (αMS) obtained by a radical polymerization reaction initiated in redo system

(potassium persulphate and sodium metabisulphite).The main characteristics of PAN fiber are:

finesse 3.3 den, saturation index SF =1.88, weight average viscosimetric molecular weight,

Mv=45485 g mol-1

; number average molecular weight, Mn= 780 per mol; polydisperse index,

Mw/Mn= 67.48 and 66.1% light remission degree. The PAN fibers (in pales form) were prepared

for experiments through a cleaning process performed with 5 g/L non-ionic surfactant (Lavotan

DSU from Bezema company) at 60°C, 60 minutes time period. The samples were then cooled,

rinsed with deionized hot water and dried at room temperature.

2) CS used in surface grafting stage is a highly viscous natural polymer. CS is a linear amino-

polysaccharide composed of approximately 20% β 1, 4-linked N-acetyl-D-glucosamine and 80%

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β 1, 4-linked D-glucosamine. The amine groups from CS have a pKa in the range of 6.2 ÷6.8,

such that the material acts as a cationic polyelectrolyte under acidic conditions.

The characteristics of CS are: degree of deacetylation, DD =78%, average molecular weight,

Mw=409,100 g mol-1

; number average molecular weight, Mn= 189,900 g mol-1

; z average

molecular weight, Mz=110,500 g mol-1

, Mw/Mn= 2.154, number average mean square radius, Rn

=49.2, radius weighted average mean square, Rw = 67.0, z average mean square radius,

Rz=108.4.

Through the solubilization of CS in 2% acetic acid solution (at room temperature) many NH2

groups were transformed in ionic groups (as NH+

3 -OOC-CH3).

S2. FTIR Analysis

S2.1. Spectral Subtraction Method

In order to perform the spectral subtraction, it was necessary that, prior to the

collection/recording of those spectra, to subtract the spectra afferent to the working medium (air)

and to ATR crystal. In processing the recorded spectra, the following operations were carried

out: atmosphere correction (CO2, water), straight line generation (for frequence range 2400-

2300, for CO2) smoothing (with the value of smoothing point of 9 for less denticulated

spectra, and higher than 9 for those very denticulated), baseline correction (concave Rubberband

algoritm), normalization, final smoothing and saving in %transmittance, as Galactic type spectra.

In order to obtain precise results, an exact spectra overlapping and linearization were necessary,

as well as and a correspondence of data points to the same x-values (equidistance and the same

resolution (4 cm-1

)) . For spectra linearization, other two baseline corrections with polyline

algorithm (one manually and one automatically performed by the software) were carried out.

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Other utilized algorithms (standard normal variate correction and detrending) permitted the

correction of drifted baseline and removing offset and tilting of spectra.

The mathematical equation (eq.S2) and the parameters used in the spectral subtraction are:

Asample spectrum - F x A reference spectrum = result (S2)

where: Asample are the absorbances of analized sample; A reference spectrum are the absorbances of the

sprectrum afferent to reference sample; F= scalar factor; the intensities of the reference sample

are scaled by the scaling factor in advance, by the software. Practically, F is indicated by the

software from the comparison between degree of the concentration/absorbance of known

components located both in the spectrum of the analyzed sample and in the reference spectrum.

In this paper, the scalar factor was 1, and during the subtraction operation we took into account

the entire spectra (within the range 4000-600cm-1

wavenumbers, with a number of points equal to

1764, XYPE =1 , YTYPE=128 and data spacing of 1,9288157685762901).

In order to highlight the absorbance bands given by each functionalization treatment, the

spectrum corresponding to untreated PAN was subtracted from that of the functionalized sample.

The absorbance bands due to the grafting treatment were calculated as the difference between the

intensities of the spectrum of the grafted sample (grafted on a certain functionalized support) and

the intensities of the spectrum of the same functionalized sample (the scalar factor was 1, too).

When the result of the subtraction had higher values (positive values), it meant that the

absorbance intensities of the analyzed sample were bigger than those of the reference sample.

When the reference sample had higher values of the absorbance intensity (or other additional

bands) than the analyzed sample, bands located below the zero line (negative values) appeared

on the difference spectrum.

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S2.2. Frequencies Characteristic of Untreated PAN fiber

Table S3. Frequencies characteristic of untreated PAN fiber

*PAN is a ternary copolymer AN+AV+αMS; AN= acrylonitrile copolymer; AV= copolyvinyl acetate;

MS= copolystyrene;

* frequencies characteristic of untreated PAN fiber were carried out using AnalyzeIT Polymer IR software / KnowItAll

from Bio-Rad Laboratories;

*(s, m or w) = strong, medium respectively weak intensity.

Bond Range [cm

-1]

Absorption [cm

-1]

Peak in Figs. 3-7.

Mode Notes: Provenience; ( Intensity)

CH 2980-2880 2933.3 2930 stretching AN; (w)

CH3 2975-2950 2955 2930 Asymmetric stretching AV; (w) and MS (m)

CH2 2940-2915 2930.0 2930.0 2917

2930 Asymmetric stretching Asymmetric stretching Asymmetric stretching

AN; (s) MS; (m) AV; (w)

CH 2890-2850 2886 2880

2930

Stretching Stretching

AV; (w) MS; (s)

CH3 2885-2855 2857 2857 Symmetric stretching AV; (w) and MS (m)

CH2 2870-2740 2857 2855 2842

2857 Symmetric stretching Symmetric stretching Symmetric stretching

MS; (m-w) AN; (m-s) AV; (w)

CN 2260-2220 2239 2239 Stretching AN; (s)

C=O 1750-1725 1732 1732 Symmetric stretching AV; (s)

C=O 1650-1550 1626 1626 Asymmetric stretching AV; (m)

Ph-R 1615-1590 1596 1626 Ring vibration C=C stretching from MS; (m-w)

Ph-R 1590-1510 1583 1626 Ring vibration C=C stretching from MS; (w)

Ph-R 1510-1440 1507 1507 Ring vibration C=C stretching from MS; (s)

-CH2- 1480-1440 1457 1451 1444.7

1444.7

Symmetric Deformation Asymm. Deformation Deformation

AV; (m) MS; (m-w) AN; (s)

Ph-R 1465-1440 1444.7 1444.7 Ring deformation C=C stretching from MS; (s)

CH3 1465-1440 1451.4 1444.7 Asymmetric deformation

AV (m) and MS; (m-w)

CH3 1390-1360 1376.2 1366

1366 Symmetric stretching Symmetric deformation

MS; (m-w) AV; (m)

C-O-C 1280-1100 1233 1233 Stretching AV; (s)

C-O 1110-1030 1069 1069 Stretching AV; (m)

Ph-R 1035-1010 1032 1032 Ring deformation =CH in-plane deformation MS; (m)

Ph-R 940-900 900 900 Ring deformation CH out-of-plane deformation MS; (w)

Ph-R 775-730 749 749 Ring deformation 5 adjacent H out of-plane deformation MS; (s-w)

Ph-R 710-670 693 693 Ring deformation CH out-of-plane deformation MS; (s-m)

Ph-R 560-530 542 542 Ring deformation Out-of-plane deformation from MS;(m-w)

C-CN 560-525 542 542 Deformation In-plane AN; (w)

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S.2.3. Results of Spectral Subtraction for Grafted Samples

Figure S4. FTIR spectra: a) spectra overlapping for C and C.CS; b) the result of spectral substraction.

C is PAN functionalized with DHEA+NaOH; C.CS is CS grafted onto C.

Figure S5. FTIR spectra: a) spectra overlapping for D and D.CS; b) the result of spectral substraction.

D is PAN functionalized with HA; D.CS is CS grafted onto D.

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Figure S6. FTIR spectra: a) spectra overlapping for E and E.CS; b) the result of spectral substraction.

E is PAN functionalized with HA+NaOH; E.CS is CS grafted onto E.

S.3. SEM Analysis

The pretreatment performed only with NaOH was the most aggressive one; it determined an

important destruction of PAN fiber observable in Fig.10.b and sustained by mass loss and also

by diminution of the peaks ascribed to the C-C bond (Figs.3, 5 and 7). Grafting of CS onto

functionalized PAN was highlighted in Fig. 10.c.

The DHEA amine determined destructions at level of ester group from AV that was dislocated

and eliminated from PAN. In the same reaction medium, DHEA was added to PAN through

amination reactions occurred at CN groups. This fact was highlighted in Fig.10.d. By means of

CS grafting onto these samples, some holes produced by DHEA were covered; this led to the

modifications in hygroscopicity and hydrophilia.

The HA amine (though it has a weaker basicity than DHEA), has a smaller molecular volume

and can easily penetrate the PAN fiber, determining modifications of the chemical and physical

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structure. Fig.10.h shows the presence of small pores as proof of the modification of physical

structure through functionalization with HA. In grafting stage, CS binds through etheric bonds to

functionalized sample and the surface appearance of fiber from Fig. 10.i proves the accumulation

of CS.

HA + NaOH mixture acted according to the mechanism presented in Fig.1; in the first stage, the

saponifications of acetate groups, respectively hydrolysis of CN groups took place. The newly

formed COOH groups (from CN) served as supports for addition of nucleophile HA agent, from

an N-acylation reaction. The aspect on fiber’ surface was characterized by the presence of

numerous white spots that are almost uniformly distributed (Fig.10.j). Fig. 10.k shows that CS is

stretched almost uniformly, like a thin film, on the surface of functionalized fiber and it covers

some of the pores created through saponification. This process determined a smaller accessibility

than in the case of PAN functionalized with HA and grafted with CS.

S4. Nitrogen (N) Content

For the pretreatment DHEA±NaOH or HA±NaOH systems, even if chemical modifications

occurred, no modification of %N was noticed, since each CN group from the initial sample was

transformed in an amide group or a group of hydroxamic acid type (which have each one N atom

in their molecule, the same as the CN group from the initial AN). In the NaOH case, the smaller

%N values led to the supposition that NaOH determined the generation of carboxylic groups

which have no N in their molecule. It is known that the CN group was transformed in carboxylic

group via amide group; the fact that at120 minutes, the %N slightly increased, can be explained

by the existence of some amide groups still unconverted into carboxylic groups. Therefore, at

120 minutes a mixture of carboxylic and amide groups can be found.

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S.5.Yellowness Index and Color Measurements

Due to pretreatments with these five reagents (NaOH, DHEA, DHEA + NaOH, HA and HA +

NaOH), chemical and physical modifications of the PAN structure took place and these can be

seen in the yellowing of all the functionalized samples, especially with amines.

The most important yellowish tint was observed in case of HA + NaOH and HA respectively

(Fig.S7), probably because of the important changes appeared in the acetate and CN groups from

PAN.

0

10

20

30

40

50

60

Witnesssample

NaOH DHEA DHEA+NaOH HA HA+NaOH

Yello

wness i

ndex,

YI

Reagents for functionalizations

2.5%reagent; 30 minutes

5%reagent; 30minutes

0

5

10

15

20

25

30

35

40

Witnesssample

NaOH DHEA DHEA+NaOH HA HA+NaOH

Yel

low

ness

ind

ex,

YI

Reagents for functionalizations and CS graftings

0%CS; 60 minutes

2.5%CS; 60 minutes

4%CS; 60 minutes

Figure S7. Yellowness Index values for samples functionalized (2.5% reagent and 0% CS) and grafted

with CS (with 2.5% respectively 4% CS).

DHEA and NaOH (as well as their mixture) determined functionalization of PAN fiber

evidenced by YI indices higher than for the witness sample. When the concentration of amine

a)

b)

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was doubled at 5% (Fig.S7.a), an increase in YI appeared because of the intensification of

chemical and physical transformations in functionalized PAN. These changes were significant in

the cases of aminations with HA+NaOH and HA and insignificant in other cases, whence the

hypothesis that HA (although being a weak base) could cause serious chemical changes to the

acrylic fiber.

CS grafted onto functionalized PAN determined a decrease of YI, probably because CS was

stretched like a film over functionalized fibers (Fig.S7.b).The increase in concentration of CS

used for grafting (from 2.5 to 4%) determined the decrease of YI in case of all tested samples.

Even if it is an amine (but a weak and colorless amine in the solved form), CS diminished the

yellowish tint acquired through functionalization for all the tested systems. By covering every

functionalized sample with a colorless film (CS), the chromatic parameters (a* and b*), as well

as the lightness (L*) were modified. In fact, a decrease of the chromatic parameter (b*) and an

increase of lightness (L*) occurred, resulting in YI diminution. These variations were also

validated by CIE Lab graphics (Fig.S8) realized by using both daylight and a standard

illuminant, D65/10°.

Fig.S8.a shows that through pretreatments realized with 2.5 % reagents, for 120 minutes, all

samples get a yellow tint, having the chromatic parameter b*>0. The most noticeable yellowing

was produced by the HA+NaOH mixture which has b*=37.116 (abbreviated with g from

figure). By doubling the reagents concentration to 5% (Fig.S8.b), the sample yellowish tint

intensified (especially for samples abbreviated with g, f and e; for example, sample g got b*=

41.673).

CS grafted onto any functionalized PAN resulted in a significant decrease of yellowing; for

example, the same sample g, got b*= 21.080 (Fig.S8.c).

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b =witness sample;

c=2.5%NaOH;

d=2.5%DHEA;

e=2.5%DHEA+2.5%NaOH;

f=2.5% HA;

g=2.5%HA+2.5%NaOH.

b=witness sample;

c=2.5%NaOH;

d=5%DHEA;

e=5%DHEA+2.5%NaOH;

f=5%HA;

g= 5%HA+2.5%NaOH.

b=witness sample;

c=(2.5%NaOH)+2.5%CS;

d=(2.5%DHEA)+2.5%CS;

e=(2.5%DHEA+2.5%NaOH)+2.5%CS

f=(2.5%HA)+2.5%CS;

g= (2.5%HA+2.5%NaOH)+2.5%CS.

Figure S8. CIE LAB graphs (D65/10). a) 120 minutes functionalization with 2.5% reagents; b) 120

minutes functionalization with 5% reagents; c) 120 minutes functionalization with 2.5 % reagents +

grafting with 2.5% CS.

a)

c)

b)

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S6. Tensile strength

Table S9. Values of weight variation and tensile strength of fibers after functionalization/

grafting

*A÷E are functionalized samples, in the form of fibers (same legend as in Fig.1);

*W.VF is weight variation after functionalization; the signs - and + represents the loss/enrich of weight;

*T.SF and T.SG are tensile strengths of fibers after functionalization (30 minutes period time) / grafting.

S7. Fastness properties

Table S.10. Color fastness to rubbing

Functionalization recipe

Dyeing after functionalization Dyeing after CS grafting

1 g/L AR 88 1 g/L AV48 1 g/L AR 88 1 g/L AV48

D.R W.R D.R W.R D.R W.R D.R W.R

2.5%NaOH 4-5 4 4-5 4-5 4-5 4-5 5 4-5

2.5%DHEA 4-5 4-5 4-5 4-5 5 4-5 5 4-5

2.5%DHEA+2.5%NaOH 4-5 4-5 4-5 4-5 5 4-5 5 4-5

2.5%HA 4-5 4-5 4-5 4-5 5 4-5 5 4-5

2.5%HA+2.5%NaOH 4-5 4-5 4-5 4-5 5 4-5 5 4-5

*D.R and W.R are dry and wet rubbing fastness, respectively.

Support

W.VF (%)

T.SF [N ]x10

-2 T.SG [N]x10

-2

witness sample

- 14.90±0.10 14.90±0.10

A -0.89±0.03 14.05±0.05 14.77±0.02

B -0.77±0.02 14.23±0.08 14.84±0.05

C -0.60±0.04 14.30±0.06 15.01±0.04

D +0.32±0.01 15.13±0.02 15.79±0.03

E -0.34±0.02 14.78±0.06 15.38±0.07