Synthesis and characterization of a new thermosensitive chitosan–PEG diblock copolymer

A novel thermosensitive hydrogel was synthesized by block copolymerization of monomethoxy poly(ethylene glycol) macromere (PEG) onto chitosan backbone, using potassium per sulfate as a free radical initiator. This block copolymer exhibits a thermoreversible transition from an injectable solution at low temperature to a gel at body temperature. Synthesized copolymers were characterized using FT-IR, 1H NMR, 13C NMR, and DSC techniques. Solubility test was performed to compare water and organo-solubility of chitosan before and after copolymerization. Sol–gel transition behavior was investigated using the vial inversion method and viscosity measurements. The gelation behavior makes the chitosan–PEG block copolymers more promising and attractive materials for biomedical applications.