Spectroscopic Study of the Interaction of Reactive Dyes with Polymeric Cationic Modifiers of Cotton Fabrics  
[PERSON]  
1 Foundation for Research and Technology--Hellas (FORTH), Institute of Chemical Engineering Science (ICE-HT), Sadiou St., GR-26504 Patras, Greece; [EMAIL_ADDRESS] (K.P.); [EMAIL_ADDRESS] (L.S.); [EMAIL_ADDRESS] (G.A.V.)  
[PERSON]  
1 Foundation for Research and Technology--Hellas (FORTH), Institute of Chemical Engineering Science (ICE-HT), Sadiou St., GR-26504 Patras, Greece; [EMAIL_ADDRESS] (K.P.); [EMAIL_ADDRESS] (L.S.); [EMAIL_ADDRESS] (G.A.V.)  
[PERSON]  
3 Department of Chemistry, University of Patras, GR-26504 Patras, Greece  
[PERSON]  
1 Foundation for Research and Technology--Hellas (FORTH), Institute of Chemical Engineering Science (ICE-HT), Sadiou St., GR-26504 Patras, Greece; [EMAIL_ADDRESS] (K.P.); [EMAIL_ADDRESS] (L.S.); [EMAIL_ADDRESS] (G.A.V.)  
[PERSON]  
2 Department of Chemical Engineering, University of Patras, GR-26504 Patras, Greece  
Footnote 1: email: {c.c.  
drawbacks, such as uneven dyeing and poor thermal stability [17], in addition to toxicity or unpleasant odor.  
Cationic polyelectrolytes have been also proposed as cationic cotton modifiers [18; 19; 20; 21; 22; 23; 24]. In most cases, covalent attachment of polymer onto the cellulose surface is assured through cellulose-initiated polymerizations [25; 26; 27; 28; 29; 30] and rarely on the reaction of cellulose with cationic copolymers bearing reactive units, like glycidyl methacrylate (GMA) [6].  
We have recently shown [31] that properly designed cationic copolymers based on 4-vinyl benzyl chloride (VBC) may be effectively used as cationic cotton modifiers. In fact, the partial cationization of VBC with triethylamine, TEAM, leads to bifunctional cationic copolymers P(VBC-co-VBCTEAMx) of VBC with 4-vinyl benzyl triethylammonium chloride, VBCTEAM (Scheme 1c). The bifunctional operation of these polymers allows their partial chemical bonding with cellulose through the VBC units and ensures; on the other hand, they have strong dyeing capabilities through the cationic VBCTEAM units. Hence, the molar ratio between VBCTEAM and VBC segments designates dye uptake of the modified fabric and modifier grafting on cellulose accordingly. Polymers offer additional properties with respect to other low molecular weight cationic modifiers not only by assuring more uniform dyeing, lower processing costs, and stability but because their structure may be manipulated in order to accomplish grafting/dye uptake/other, e.g., antimicrobial properties with optimal performance.  
To further improve cotton dyeing processes, a major challenge is to get a deeper understanding of cationic modifier--dye interactions. To this end, we took advantage of a variety of spectroscopic techniques, such as UV-Vis and fluorescence spectroscopies, ATR-FTIR vibrational spectroscopy, and X-Ray Photoelectron spectroscopy (XPS), for the study of binary dye-polymer mixtures both in aqueous solution and in a solid state, as well as of cationized cotton substrates dyed with reactive dyes. To elucidate the influence of the charge density of the cationic modifier, the homopolymer poly(4-vinyl benzyl triethylammonium chloride), PVBCTEAM (Scheme 1c, x = 0), and the copolymer P(VBC-co-VBCTEAM53) containing 53% mol VBCTEAM units (Scheme 1c, x = 53) were selected. Moreover, in order to explore the importance of the charge density of the dye, the reactive dyes Novacron Ruby S-3B and Remazol Brilliant Blue R bearing two and five negatively charged groups, respectively, were chosen for the study.