Preparation and characterization of chitosan-graft-poly (ε-caprolactone) with an organic catalyst

Chitosan-graft-poly(epsilon-caprolactone) was prepared via the ring-opening graft polymerization of epsilon-caprolactone (CL) through chitosan with 4-dimethylaminopyridine as a catalyst and water as a swelling agent. The graft content of PCL within the graft copolymer was adjusted by the feed ratio of CL to chitosan, and the highest grafting concentration of PCL was up to about 400%. Fourier transform infrared, H-1 NMR, and two-dimensional heteronuclear single quantum coherence analyses indicated that the amino group (NH2-CH-2) of chitosan initiated the graft polymerization of CL through the backbone of chitosan, and the hydroxyl group (HO-CH(2-)6) of chitosan did not participate in initiating the graft polymerization. The percentage of amino groups initiating the graft polymerization decreased with an increasing molar ratio of CL to chitosan in the feed, and this was attributed to the fact that the graft polymerization system increasingly became heterogeneous with an increasing feed ratio of CL to chitosan. The physical properties of the graft copolymers were characterized by thermogravimetric analysis and wide-angle X-ray diffraction, respectively. These suggested that the introduction of PCL grafts through the chitosan backbone would to some extent destroy the crystalline structure of chitosan, and the PCL grafts existed in an amorphous structure. (c) 2006 Wiley Periodicals, Inc.