Synthesis and characterization of n-vinylimidazole based semi-interpenetrating network hydrogels

In this study, semi-interpenetrating network (semi-IPN) hydrogels were synthesized with different proportions of poly(diallyldimethylammonium chloride) [p(DADMAC)] as the guest polymer whose host polymer is crosslinked poly(vinylimidazole) [p(VIm)]. Hydrogels were characterized by FTIR, SEM, TGA and swelling behaviors of them were investigated at different pH values. In addition, water release experiments were carried out at 25ºC for all gels. Semi-IPNs had higher swelling rate (S), equilibrium swelling rate (Smaks,d) and equilibrium water content (EWC) values compared to p(VIm) at all pH values; as well, increased p(DADMAC) amount were found to increase these values even more. The pH of the medium had a significant effect on the swelling behavior of the hydrogels. At pH 2, all gels were both faster and more swollen with higher EWC values. At this pH value, all gels reached almost Smaks,d in about 3000 minutes, while this time reached 6000 minutes at pH 12. Smaks,d, which was 4.13 g water/g gel for homopolymer at pH 6.2, reached 12,58 g water/g gel with an increase of 205% for semi-IPNs. At the same pH, the EWC value increased by 15.7% from 0.80 g water/g gel to 0.93 g water/g gel. p(VIm) releases about 85% of the retained water within 4300 minutes, while this value has increased up to 93% for semi-IPNs in the same time period.