Microwave-assisted graft copolymerization of ε-caprolactone onto chitosan via the phthaloyl protection method

The graft polymerization of ε-caprolactone onto chitosan was carried out smoothly under microwave irradiation, via a protection-graft-deprotection procedure with phthaloylchitosan as precursor and stannous octoate as catalyst. The chemical structure of the obtained chitosan-g-polycaprolactone was characterized by FT-IR and NMR spectroscopy. By microwave irradiation, the chitosan-g-polycaprolactone with high grafting percentage above 100% was achieved in rather short time. And the graft copolymerization was greatly improved at the higher power outputs of 450 and 600 W in the studying range. After deprotection, the phthaloyl group was removed and the amino group was regenerated. Thus, the chitosan-g-polycaprolactone copolymer was an amphoteric hybrid with both a large amount of free amino groups and hydrophobic polycaprolactone side chains.