Swelling behavior of thermoreversible poly(N-isopropylacrylamide-co-N-vinylimidazole) Hydrogels

Thermoresponsive hydrogels based on N-isopropylacrylamide and N-vinylimidazole were synthesized, and their swelling-deswelling behavior was studied as a function of the total monomer concentration. For co-polymeric structures with better thermoresponsive properties with respect to poly(N-isopropylacrylamide-co-N-vinylimidazole) hydrogels, these hydrogels were protonated with HCl and HNO₃, and the copolymer behaviors were compared with those of the unprotonated hydrogels. The temperature was changed from 4 to 70°C at fixed pHs and total ionic strengths. The equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all the hydrogels.