Synthesis and characterization of dextran grafted with poly(N-isopropylacrylamide-co-N,N-dimethyl-acrylamide)

Graft copolymers consisting of dextran as a main chain and poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAAm-co-DMAAm)) as graft chains were synthesized. For the synthesis of the graft copolymers, a semitelechelic poly(NIPAAm-co-DMAAm) with an amino end-group was obtained by radical copolymerization with ethanethiol as a chain transfer agent, followed by a coupling reaction of its hydroxyl end-group with ethylenediamine. Graft copolymers with various length of the grafts were obtained from coupling reactions between carboxymethyl dextran and poly-(NIPAAm-co-DMAAm) in the presence of a water-soluble carbodiimide. The graft copolymers in phosphate buffer exhibit lower critical solution temperatures due to thermosensitivity of their grafts. There is no significant change in the hydration-dehydration behavior of the poly(NIPAAm-co-DMAAm) chain after the grafting reaction. The existence of such grafts in dextran may play an important role for modulated degradation in synchronization with temperature.