Roles of Novel Reactive Cationic Copolymers of 3-Chloro-2-hydroxypropylmethyldiallylammonium Chloride and Dimethyldiallylammonium Chloride in Fixing Anionic Dyes on Cotton Fabric

e roles of novel reactive cationic copolymers (P(CMDA-DMDAAC)s) of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride (CMDA) and dimethyldiallylammonium chloride (DMDAAC) in �xing anionic dyes on cotton fabric were studied by modern instrumental analysis technologies such as FT-IR spectra and SEM analysis, to achieve the new theoretical guides for the wide applications of those dye �xatives. e FT-IR spectra of the obtained insoluble-water color lakes veri�ed that they could be formed from the electrostatic interactions of the P(CMDA-DMDAAC)s with anionic dyes, which were further con�rmed by the FT-IR analysis of the anionic dyes on dyeing cotton sample �xed by P(CMDA-DMDAAC)s. e FT-IR spectra of cotton samples �xed by P(CMDA-DMDAAC)s showed the absorptions of P(CMDA-DMDAAC)s and the signs similar to the formation of new ether linkage on cotton fabric even a�er being repeatedly washed, which were further con�rmed by the SEM analysis of the �xed dyeing cotton samples. us, the reactive units (CMDA) of the obtained P(CMDA-DMDAAC)s could be expected to bring about the covalent bonds with the hydroxyl groups of cotton (cellulose) to form an ether linkage when �xing, resulting in the stronger interactions of P(CMDA-DMDAAC)s with cotton fabric, as well as their electrostatic forces with anionic dyes to produce the insoluble-water color lakes, for the development of fastness of anionic dyes on cotton fabric.


Introduction
Cotton fabric is the most widely welcomed textile in the world, which is mainly made of cellulose [1].Dyed cotton should have high colorfastness to usual repeated domestic launderings [2].
By now, poly (dimethyldiallylammonium chloride) (PDMDAAC), which is the polymer derived from radical homopolymerization of dimethyldiallylammonium chloride (DMDAAC), has been used as the optimum dye �xatives with a view to enhance the uptake of anionic dyes on cotton fabric, and the mechanism of interactions involved can be theoretically interpreted by the participation of electrostatic forces between the dyes and the basic cationic groups in the polymer to reduce the dyes' water-soluble abilities through the formation of color lakes [3,4].However, it appears that no con�rmation of the interpretation has been carried out by modern instrumental analysis technologies.Moreover, the cellulose and dimethyldiallylammonium chloride have the similar units of conformational structures in main chains, which would be expected to contribute to close interactions of Van der Waals forces when �xing; thus, PDMDAAC can be widely applied in the �xing of different dyes on cotton fabric [5][6][7][8].However, the development of PDMDAACtreated dyes' rubbing fastness especially wet rubbing fastness is limited; this might be due to the possible dissociation of some of color lakes based on electrostatic forces which are caused by the effect of water molecules and the interactions of Van der Waals forces between PDMDAAC and cotton fabric which are also easy to be destroyed by external forces [9].is promotes researchers to select new series of PDMDAAC-based dye �xatives for further improving the fastness properties of anionic dyes on cotton fabrics.Some researches indicated that the dye-�xing performances of polycationic dye �xatives could vary from their different molecular weights [10][11][12], and in our contribution, the authors discovered that those PDMDAAC dye �xatives with the controlled molecular weights characterized by intrinsic viscosities of 0.24-0.47dL/g could exhibit better dye-�xing performances [13].On the other hand, if lower contents (below 20% molar contents) of reactive units, which can bring about the covalent reactions with the hydroxyl groups of cotton (cellulose) to form a stronger �xing interaction with cotton surface, are incorporated into the backbones of PDMDAAC, the dye-�xing performances of those modi�ed PDMDAAC can also be improved [14].In view of these points in our contribution, a series of novel reactive cationic copolymers of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride (CMDA) and dimethyldiallylammonium chloride (DMDAAC), (P(CMDA-DMDAAC)s) (PDMDAAC-based dye �xatives) with controlled structures of 2%-20% CMDA molar contents in main chains and controlled intrinsic viscosities of 0.15∼0.76dL/g, which were designed as more useful PDMDAAC-based dye �xatives and derived from the further incorporation of below 20% molar contents of reactive units (CMDA units) into the backbones of the PDMDAAC with the controlled intrinsic viscosities of 0.24-0.47dL/g or nearly, were successfully synthesized (Scheme 1) [15].However, the information about roles of novel P(CMDA-DMDAAC)s in �xing anionic dyes on cotton fabric was very limited and especially it has not been veri�ed by modern instrumental analysis in open literature yet.us, in this paper, a series of experiments were designed to con�rm the roles of novel P(CMDA-DMDAAC)s in �xing anionic dyes on cotton fabric such as the �xing interactions of P(CMDA-DMDAAC)s with anionic dyes and cotton fabric, by modern instrumental analysis technologies [FT-IR spectra and Scanning Electron Microscopy (SEM)], to achieve the new theoretical guides for the wide applications of those PDMDAAC-based dye �xatives.

Experimental
2.1.Materials and Measurement.All the selected novel P(CMDA-DMDAAC)s in this paper could be synthesized by the copolymerization of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride (CMDA) and dimethyldiallylammonium chloride (DMDAAC), and by varying molar ratios of raw materials of CMDA to DMDAAC from 2/98 to 20/80 and increasing initial monomer concentrations from 19% to 40% with the decrease of initiator amount from 12% to 6% during polymerization according to the methods in the literature [15].Reactive Scarlet 3BS (industrial purity) and cotton fabric (industrial product) were both collected and stored from Jiangsu Nantong Chemicals and Textile Co., Ltd.(China).e FT-IR spectra of the products in KBr pellets (2%) were recorded using a Nicolet FT-IR (510 P) spectrophotometer.Scanning Electron Microscopy (SEM) analysis was measured with a JSM-5610 scanning electron microscopy instrument.

Roles of P(CMDA-DMDAAC)s in Fixing Anionic Dyes on
Cotton Fabric: Design and Process 2.2.1.Fixing Interactions of P(CMDA-DMDAAC)s and Anionic Dyes.As polycationic dye �xatives, the basic cationic groups of P(CMDA-DMDAAC)s were theoretically expected to form the electrostatic forces with anionic dyes and produce the water insoluble color lakes when �xing; however, these explanations have not still been con�rmed by modern instrumental analysis.us, the color lakes derived from the interactions of one P(CMDA-DMDAAC) containing higher basic cationic DMDAAC units in main chains (the molar contents of DMDAAC units in the main chains were 98%, and the intrinsic viscosity was 0.22 dL/g) with one anionic dye (Reactive Scarlet 3BS) were prepared for the studies as one example based on the widely-used basic �xing conditions of PDMDAAC-based dye �xatives on cotton fabric [13,14]; the operation processes of forming color lakes were designed and listed as follows.
According to the basic �xing weight ratios of anionic dyes to the PDMDAAC-based dye �xatives (w/w = 2/3) [13,14], to a 100 mL baker, 0.50 g Reactive Scarlet 3BS and 50 mL deionized water were added, to form a dye solution.And then 0.75 g of the P(CMDA-DMDAAC) was added with stirring to produce a lot of precipitation (color lake), the precipitation was dried, and the structure was characterized by FT-IR analysis for analyzing the formation of color lakes.

Fixing Interactions of P(CMDA-DMDAAC)s and Cotton
Fabric.According to the basic �xing conditions of reactive PDMDAAC-based dye �xatives on cotton fabric [14], one of the P(CMDA-DMDAAC)s containing higher reactive CMDA units in main chains (the molar contents of CMDA units in the main chains were 10%, and the intrinsic viscosity was 0.16 dL/g) was selected to be interacted with the undyeing cotton fabric as one example and the structure changes of the untreated and treated cotton samples were con�rmed by comparing their FT-IR analysis, for investigating the �xing interactions of P(CMDA-DMDAAC)s with cotton fabric.Moreover, two higher amounts (50% o.w.f, and 100% o.w.f) of the P(CMDA-DMDAAC)s besides the common �xing amounts (3% o.w.f) were extraused to treat the undyeing cotton fabric, in order to clearly measure the structure changes of untreated cotton sample and the treated cotton sample by comparing their FT-IR analysis.e operation processes were designed and listed as follows.
Different amounts (3% o.w.f, 50% o.w.f, and 100% o.w.f) of the P(CMDA-DMDAAC)s were selected to treat the cotton fabric (undyeing) at 60 ∘ C for 30 min, the pH of �x application was 7, the liquor ratio was 1 : 20, and some of the treated cotton samples were directly washed with water for approximately 4-5 times to a constant weight for investigating the �xing interaction strengths of the P(CMDA-DMDAAC) with cotton fabric and were dried at 50 ∘ C for 24 h to be characterized by FT-IR analysis.e treated cotton samples at normal �xing temperature (60 ∘ C) were compared to those of untreated cotton sample, for comparing the structure changes of untreated and treated cotton samples.en some of another treated cotton samples (unwashed by water) were dried and further baked at 180 ∘ C for 3 min, washed with water for approximately 4-5 times to a constant weight for their �xing investigating interaction strengths of the P(CMDA-DMDAAC) with cotton fabric, and dried to be characterized by FT-IR analysis.is sample, as the treated cotton sample baked at the higher temperature, was compared to that of untreated cotton sample, for comparing the structure changes of untreated and treated cotton samples at the normal �xing temperature.

Fixing Interactions of P(CMDA-DMDAAC)s on
Dyeing Cotton Fabric

Fixing Interactions of P(CMDA-DMDAAC)s and
Anionic Dyes on Dyeing Cotton Fabric.According to the basic dyeing and �xing conditions of reactive PDMDAACbased dye �xatives on cotton fabric (Scheme 2) [14], one of the P(CMDA-DMDAAC)s containing higher basic cationic DMDAAC units in main chains (the molar contents of DMDAAC units in the main chains were 98%, and the intrinsic viscosity was 0.22 dL/g) was selected to �x one anionic dye (Reactive Scarlet 3BS) on dyeing cotton fabric as one example.And the structure changes of the selected anionic dyes on un�xed and �xed dyeing cotton samples were con�rmed by comparing their FT-IR analysis, for investigating the �xing interactions of P(CMDA-DMDAAC)s with anionic dyes on dyeing cotton fabric.Moreover, a higher amount (100% o.w.f) of Reactive Scarlet 3BS is expected for the common dyeing amounts (2% o.w.f) and higher amounts (150% o.w.f, and 300% o.w.f) of the P(CMDA-DMDAAC)s besides the common �xing amounts (3% o.w.f) were selected, in order to clearly measure the structure changes of dyes on dyeing cotton fabric by comparing their FT-IR analysis.e operation processes were designed and listed as follows.
As shown in Scheme 2, the cotton fabric was dyed with 100% (o.w.f) Reactive Scarlet 3BS at 60 ∘ C, and then different amounts (3% o.w.f, 150% o.w.f, and 300% o.w.f) of the P(CMDA-DMDAAC)s were respectively selected to �x the selected anionic dye on the dyeing cotton fabric at 60 ∘ C for 30 min, the p� of �x application was �, the li�uor ratio was 1 : 20, and then the �xed dyeing cotton samples were dried to be characterized by FT-IR analysis for comparing the structure changes of the un�xed dyeing cotton fabric and dyeing cotton fabric �xed by the P(CMDA-DMDAAC).

Fixing Interactions of P(CMDA-DMDAAC)s and
Dyeing Cotton Fabric.According to the basic dyeing and �xing conditions of reactive PDMDAAC-based dye �xatives on cotton fabric [14], one of the P(CMDA-DMDAAC) containing higher reactive CMDA units in main chains (the molar contents of CMDA units in the main chains were 10%, and the intrinsic viscosity was 0.16 dL/g) was used to �x the dyeing cotton fabric as one example and the surface morphologies of un�xed dyeing cotton sample and the P(CMDA-DMDAAC)-�xed dyeing cotton samples were con�rmed by comparing their Scanning �lectron Microscopy (S�M) analysis, for further investigating the �xing interactions of P(CMDA-DMDAAC)s with dyeing cotton fabric.e operation processes were designed and listed as follows.As shown in Scheme 2, the cotton fabric was dyed with 2% (o.w.f) Reactive Scarlet 3BS at 60 ∘ C, and then 3% (o.w.f) of the P(CMDA-DMDAAC)s were used to treat the cotton fabric dyed with Reactive Scarlet 4BS at 60 ∘ C for 30 min; the pH of �x application was 7; the li�uor ratio was 1 : 20; moreover, the �xed dyeing cotton sample was dried at room temperature and then further baked at 180 ∘ C for 3 min [14].Finally, Scanning Electron Microscopy (SEM) analysis was used to characteri�e the surface morphologies of un�xed dyeing cotton sample and the P(CMDA-DMDAAC)-�xed dyeing cotton sample [16].

Interactions of P(CMDA-DMDAAC)s and Anionic Dyes.
As mentioned in Section 2.2.1, the FT-IR analysis of color lakes derived from the interaction between one P(CMDA-DMDAAC) (the molar contents of CMDA units in the main chains were 2%, and the intrinsic viscosity was 0.22 dL/g) and Reactive Scarlet 3BS was shown in Figure 1.
Figure 1 showed the FT-IR spectra of the color lakes had the absorptions at approximately 728 cm −1 -1032 cm −1 which were similar to those of Reactive Scarlet 3BS, indicating that their structures consisted of dyes (Reactive Scarlet 3BS), and had the absorptions of the -CH 3 groups at 3039 cm −1 , the absorptions of the -CH 2 -linkage at 2936 cm −1 , and the absorptions of the methyne linkage at 2863 cm −1 , which were similar to those of P(CMDA-DMDAAC), indicating that their structures consisted of the P(CMDA-DMDAAC) (Peak 1).
us, it could be concluded from the above-mentioned results that the basic cationic groups of the obtained P(CMDA-DMDAAC)s would form electrostatic forces with anionic dyes to produce the insoluble-water color lakes.

Interactions of P(CMDA-DMDAAC)s and Cotton Fabric at Normal Fixing Temperatures.
As mentioned in Section 2.2.2, the FT-IR analysis of untreated cotton samples and the cotton samples treated by the P(CMDA-DMDAAC)s at normal �xing temperatures was shown in Figures 2 and 3.
Figure 2 showed the FT-IR spectra of the untreated cotton fabric had the absorption of the OH group at 3349 cm −1 , the absorption of the -CH linkage at 2901 cm −1 , the absorption of the -CH 2 -group at 1435 cm −1 , and the absorption of the C-O-C group at 1029 cm −1 , 1053 cm −1 , 1108 cm −1 , and 1160 cm −1 , indicating that cotton fabric was mainly made of cellulose [16].
As well as the similar absorptions to the untreated cotton fabric, the FT-IR spectra of the cotton samples �xed by the P(CMDA-DMDAAC) further showed the new absorptions at 1428 cm −1 of the P(CMDA-DMDAAC) (Peak 2); moreover, the absorptions at 1053 cm −1 (Peak 1), 1640 cm −1 (Peak 3), and 3349 cm −1 (Peak 4) were all increased with the increase of the amount of P(DHAC-DMDAAC), because the P(CMDA-DMDAAC) had also the similar absorptions at those shis, which would increase the intensity of the similar absorptions.us, all these results suggested that the P(CMDA-DMDAAC)s could be penetrated into cotton fabric and be convenient to interact with anionic dyes when �xing.
However, aer being adequately washed with water to a constant weight (Figure 3), the new absorptions of the P(DHAC-DMDAAC) at 1428 cm −1 would be absent, and the increased absorptions (1053 cm −1 , 1640 cm −1 , and 3349 cm −1 ) were all decreased so that they were similar to those of untreated cotton fabric, possibly indicating that most of the interactions of the P(DHAC-DMDAAC) and cotton fabric were attributed to Van der Waals forces at lower �xing temperatures (only 60 ∘ C), which were very weak [5].

Interactions of P(CMDA-DMDAAC)s and Cotton Fabric
Baked at Higher Temperatures.As mentioned in Section 2.2.2, the FT-IR analysis of untreated cotton sample and the cotton sample treated by P(CMDA-DMDAAC)s baked at 180 ∘ C was shown in Figure 4.
Figure 4 showed as well as the similar absorptions to the untreated cotton fabric, compared to the results at normal �xing temperatures (Figure 3), even if being washed with water for approximately 4-5 times to a constant weight, the FT-IR spectra (Curve "c" and Curve "d") of the cotton samples �xed by the P(CMDA-DMDAAC) further showed that the absorption intensity of the P(DHAC-DMDAAC)treated cotton sample at 1053 cm −1 (Peak 1) was higher than that of untreated cotton fabric (Curve "a"); this might be due to the formation of new C-O-C linkage, derived from the reaction linkage between the reactive units (CMDA) of the obtained P(CMDA-DMDAAC)s and the hydroxyl groups of cotton (cellulose), resulting in the increase of the intensity of the similar absorptions.In addition, the absorptions at 1429 cm −1 (Peak 2), 1640 cm −1 (Peak 3), and 3349 cm −1 (Peak 4) were still increased with the increase of the amount of P(CMDA-DMDAAC) as similar as shown in Figure 2; further indicating that a strong interaction could link the P(CMDA-DMDAAC) and the cotton fabric.us, it could be concluded from the above-mentioned results that the reactive units (CMDA) of the obtained P(CMDA-DMDAAC)s could be possibly expected to bring about covalent bonds with the hydroxyl groups of cotton (cellulose) to form a new ether linkage, resulting in the stronger interactions of P(CMDA-DMDAAC)s with cotton fabric when �xing.

Interactions of P(CMDA-DMDAAC)s on
Dyeing Cotton Fabric  Figure 5 showed, the FT-IR spectra of dyeing cotton samples had the dye's absorptions at 802 cm −1 , 1456 cm −1 , and 1543 cm −1 , and the absorption of dye's sulfonate anion at 1103 cm −1 or nearly was blocked by the similar strong absorption of C-O-C linkage of cotton (cellulose).
Compared to those of un�xed dyeing cotton sample, the FT-IR spectra of the dyeing cotton sample �xed by 300% (o.w.f) P(CMDA-DMDAAC) had the absorption of the -CH 3 groups at 3022 cm −1 (Peak 1, Curve "d"), which could be attributed to the P(CMDA-DMDAAC).Moreover, the absorptions at 1456 cm −1 (Peak 3) and 1053 cm −1 (Peak 4) were both increased with the increase of the amount of P(CMDA-DMDAAC), because the P(CMDA-DMDAAC) had also the similar absorptions at the corresponding shis, which would increase the intensity of the similar absorptions.erefore, all these results further indicated that P(CMDA-DMDAAC)s could be penetrated into cotton fabric and be convenient to interact with dyes when �xing.
In addition, similar to the results of forming color lakes (Section 3.1), the FT-IR spectra of dyeing cotton samples �xed by the P(CMDA-DMDAAC)s further also showed that the absorption of the dye on dyeing cotton sample was shied from 1543 cm −1 to 1540 cm −1 (Peak 2, Curve "d" in Figure 5), which was in agreement with that of forming color lakes (Section 3.1), further indicating that the expected color lakes could be possibly formed on dyeing cotton fabric, to play a role in the development of fastness of dyes on cotton fabric.

Interactions of P(CMDA-DMDAAC)s and Dyeing Cotton Fabric.
As mentioned in Section 2.2.3.2,Scanning Electron Microscopy (SEM) analysis was used to characterize the surface morphologies of un�xed dyeing cotton sample and the dyeing cotton sample �xed by the P(CMDA-DMDAAC) (the molar contents of CMDA units in main chains were 10%, and the intrinsic viscosity was 0.16 dL/g); the results were shown in Figure 6.
Figure 6 showed, compared to the result of un�xed dyeing cotton sample, there were a lot of new surface materials possibly derived from the �xing participation of P(CMDA-DMDAAC), which closely adhered to the surface of the �xed dyeing cotton sample, indicating that they could be convenient to form the further �xing interactions of P(CMDA-DMDAAC)s with cotton fabric such as covalent bonds.

Conclusions
It could be veri�ed by the studies on the roles of novel reactive cationic copolymers (P(CMDA-DMDAAC)s) of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride and dimethyldiallylammonium chloride in �xing anionic dyes on cotton fabric, using several modern instrumental analysis technologies (FT-IR spectra and SEM analysis), that the reactive units (CMDA) of the obtained P(CMDA-DMDAAC)s could be expected to bring about the covalent bonds with the hydroxyl groups of cotton (cellulose) to form an ether linkage at higher temperature (180 ∘ C), resulting in the stronger �xing interactions of P(CMDA-DMDAAC)s with cotton fabric, besides their basic cationic groups would form electrostatic forces with anionic dyes to produce the insoluble-water color lakes, for the development of dyes' fastness on cotton fabric.

S 1 :
Preparation of novel cationic copolymers of P(CMDA-DMDAAC)s in previous work.