Amphiphilic chitosan graft copolymer via combination of ROP, ATRP and click chemistry: Synthesis, self-assembly, thermosensitivity, fluorescence, and controlled drug release

Novel amphiphilic chitosan-g-poly(ε-caprolactone)-(g-poly(2-(2-methoxyethoxy)ethyl methacrylate)-co-oligo(ethylene glycol) methacrylate) (CS-g-PCL(-g-P(MEO2MA-co-OEGMA))) copolymers with double side chains of PCL and P(MEO2MA-co-OEGMA) were synthesized via combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP) and click chemistry. The molar ratio of PCL and P(MEO2MA-co-OEGMA) was varied through variation of the feed ratio and the coupling efficiency of click chemistry is comparatively high. The graft copolymers can assemble into spherical micelles. The micelles show thermosensitive properties and the lower critical solution temperatures (LCSTs) were influenced by CS chains and the ratio of PCL and P(MEO2MA-co-OEGMA) side chains. Moreover, the micelles can reversibly swell and shrink in response to the change of temperatures. Furthermore, the micelles present obvious fluorescence and the fluorescent intensity can be adjusted by altering the temperatures. The investigation of doxorubicin release from the micelles indicated that the release rate of the drug could be effectively controlled by altering the temperatures.