Abstract
Graft copolymers of chitosan (CS) and poly(N-isopropylacrylamide) (PNIPAAm) were successfully synthesized through a two-step reaction. Chitosan was first modified with maleic anhydride in formic acid through the reaction of amino group with anhydride, thus having vinyl groups. In the second step, PNIPAAm was grafted onto CS via this vinyl groups initiated by UV radiation. The structures of graft copolymers were confirmed by FTIR and NMR analysis. The grafting efficiency increased with the added amount of NIPAAm monomer and reached a plateau value about 55%. In the mean time, grafting ratio increased linearly with the added amount of NIPAAm. A two-stage thermal degradation behavior was observed for the copolymer samples, which confirmed the structure of graft copolymers. The influences of the grafting ratio on the "pH/temperature induced" phase transition behaviors and swelling characteristics of the hydrogel system were studied. The cell viability of fibroblasts was also evaluated.
