Graft copolymers of chitosan and vinyl acetate were synthesized by free radical technique using cerium (IV) as the initiator. Under controlled conditions, as much as 92% grafting with a grafting yield of 30-40% could be achieved. Chitosan-g-poly(vinyl alcohol) copolymers were derived by the alkaline hydrolysis of the chitosan-g-poly(vinyl acetate) precursor. Thermogravimetric, FTIR, and X-ray diffraction analyses of chitosan and the copolymers confirmed the grafting reaction between chitosan and vinyl acetate and also the subsequent hydrolysis. Both the copolymers possessed very good film-forming properties. Grafting resulted in a significant increase in mechanical strength of both the copolymers in the dry condition. Chitosan-g-poly (vinyl acetate) (CH-PVAc) proved more hydrophobic than did pure chitosan, whereas chitosan-g-poly(vinyl alcohol) (CH-PVOH) exhibited enhanced hydrophilicity as evident from their swelling characteristics and contact angle measurements. The enhanced swelling of CH-PVOH was ascribed to the presence of the pendant poly(vinyl alcohol) group. At pH 1.98, the CH-PVAc copolymer films showed greater stability than do pure chitosan films, which is highly beneficial for specific biomedical applications. Both the copolymers showed lower glass transition temperature than do pure chitosan. Grafting did not affect the overall thermal stability, and the differential thermogram substantiated the grafting. The investigations indicate that the synthetic-natural hybrid copolymers having desirable mechanical properties and tailored hydrophilic/hydrophobic characteristics are realizable. These polymers could be exploited for varied biomedical applications. (c) 2007 Wiley Periodicals, Inc.