Novel N-vinylimidazole based copolymeric hydrogels: Synthesis, characterization and swelling properties

Abstract

In this study, novel N-vinylimidazole based copolymeric hydrogels were synthesized by free radical solution polymerization. In the presence of N, N'-methylenebisacrylamide and 2,2'-azo-bis-isobutyronitrile as crosslinking agent and initiator, respectively. [2-(methacryloyloxy) ethyl] dimethylpentylammonium bromide and [2-(methacryloyloxy) ethyl] dimethylbenzylammonium chloride were used as comonomer (functional monomer). They were synthesized by the quaternization of 2-(dimethylamino) ethyl methacrylate with 1-bromopenthane and 1-benzylchloride, respectively, Obtained hydrogels were characterized by using a Fourier Transform Infrared Spectrometer (FTIR) and a Scanning Electron Microscope attached with Energy Dispersive X-Ray dedector (SEM-EDX). SEM images represented porous surface morphologies of the hydrogels, moreover the presence of quaternized monomers in the copolymers were approved spectrophotometrically. The ratio of functional monomers in the polymer matrix were varied between 1% and 15%. Dynamic swelling experiments were carried out at pH 6.0 and 25 degrees C for all hydrogels and some important parameters such as swelling ratio at equlibrium (Smax), initial swelling ratio (r0), equilibrium water content (EWC) and diffusion coeficient (D) were calculeted from obtained data. The value of Smax increased up to approximately 1100% for hydrophilic functional monomer incorporated hydrogels. While the value of Smax was 4.4 g water/g hydrogel for homopolymeric poly(N-vinylimidazole), it was 52.2 g water/g hydrogel for a copolymeric hydrogel. The water transport mechanism into polymeric matrix was Fickian (diffusion-controlled) for homopolymeric and copolymeric hydrogels containing lower amount of functional monomer while the mechanism was non-Fickian for all of others, meaning that both diffusion and polymer relaxation control.