Swelling behavior of thermoreversible poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels

Abstract

Abstract 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 copolymeric structures with better thermoresponsive properties with respect to poly( N ‐isopropylacrylamide‐ co ‐ N ‐vinylimidazole) hydrogels, these hydrogels were protonated with HCl and HNO 3 , 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. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1619–1624, 2004