Synthesis and characterization of quaternary ammonium functional N-viniylimidazole based copolymer hydrogels

In this study, firstly, N-vinylimidazole based copolymer hydrogels were synthesized by free radical solution polymerization. Then, some spectrometric and microscopic techniques were applied for the characterization, and swelling behaviors of the polymers in distilled water were investigated. 2-(dimethylamino)ethyl methacrylate (DMA) and their quaternized derivatives were used as comonomer (functional monomer). Functional monomers have quaternary ammonium ions in their structures and different alkyls with varying chain length or benzyl group on these ammonium functionality. Each copolymer gel showed different swelling behavior from the others according to their chemical structure and the ratio of functional monomer in the copolymer matrix. In the presence of hydrophilic functional monomer, equilibrium swelling rate (Smax) of copolymers significantly increased, and Smax values of all copolymers were higher than that of homopolymer. 1.0 g of homopolymer absorbed 4.4 g of water, while this value increased by about 1290% to 61.3 g of water for the same amount of copolymer. Equilibrium water content (EWC) of the homopolymer was 0.815 and EWC for copolymers were mostly higher than 0.815. Some copolymer gels swell almost 12 times faster than homopolymer. The water transport mechanism into polymeric matrix was Fickian (diffusion-controlled) for copolymer hydrogels incorporated lower amount of functional monomer, as for the homopolymer.