Synthesis and self-association in dilute aqueous solution of hydrophobically modified polycations and polyampholytes based on 4-vinylbenzyl chloride

Abstract

Linear copolymers, P(MMA-co-VBC) and P(SSNa-co-VBC), of 4-vinylbenzyl chloride (VBC) with hydrophobic (methyl methacrylate, MMA) or hydrophilic anionic (sodium styrene sulfonate, SSNa) monomers were prepared through free radical polymerization. The molar content of MMA or SSNa units ranges from 0% up to 90% (mol/mol). After polymerization, VBC was quaternized using short chain (triethylamine, TEAM) or long chain (N,N-dimethylhexadecylamine, HAM) amines. FTIR and 1H NMR verified that the P(MMA-co-VBC) series were fully quaternized, leading to hydrophobic polycations P(MMA-co-VBCTEAM) or hydrophobic/hydrophobically modified polycations P(MMA-co-VBCHAM), while the P(SSNa-co-VBC) series were partially quaternized, leading to polyampholytes P(SSNa-co-VBCTEAM-co-VBC) and hydrophobically modified polyampholytes P(SSNa-co-VBCHAM-co-VBC). To overcome partial quaternization problems, hydrophobically modified polyampholytes P(SSNa-co-VBCHAM) were synthesized through direct polymerization of SSNa and vinylbenzyl dimethylhexadecylammonium chloride (VBCHAM). The solubility and self-association behavior of these copolymers in water were investigated through turbidimetry, Nile Red fluorescence probing, dynamic light scattering and ζ-potential measurements. It is found that phase separation and self-association are mostly affected by the copolymer’s net charge and not the nature of the hydrophobic or charged unit. Moreover, the introduction of cationic amphiphilic units (VBCHAM) not only favors the self-association of the final hydrophobically modified polymers, forming aggregates in aqueous solution, but may also lead to polymers with antimicrobial activity.