Preparation of thermosensitive chitosan with poly(N-isopropylacrylamide) side at hydroxyl group via O-maleoyl-N-phthaloyl-chitosan (MPCS)

A novel temperature-sensitive graft copolymer was prepared by grafting N-isopropylacrylamide (NIPAAm) onto a chitosan derivate whose amino groups were protected by phthaloyl groups. The deprotection of the phthaloyl groups yields chitosan-g-PNIPAAm copolymers with free amino groups. The chemical structure of the copolymers was characterized by FT-IR, 1H and 13C NMR spectroscopy. Our experiments reveal that the grafting degree increases with monomer concentration and reaction time but decreases with the initiator concentration and temperature. In comparison with the chitosan, chitosan-g-PNIPAAm shows a faster thermal decomposition. This is because PNIPAAm chains destroy the crystalline region of chitosan. Besides, the graft copolymers exhibit good solubility in aqueous solutions with a broader pH range. Like PNIPAAm, the copolymer exhibits a thermally sensitivity in aqueous solution.