Controlled Preparation of Physically Cross linked Chitosan-g-Poly(vinyl alcohol) Hydrogel

Physically crosslinked chitosan-g-poly(vinyl alcohol) hydrogels with controllable graft percent were prepared in three steps. Poly(vinyl acetate) (PVAc) was first grafted onto chitosan via radical copolymerization. Then the copolymer was converted into chitosan-g-poly(vinyl alcohol) by alcoholysis reaction. The graft percent of poly (vinyl alcohol) (PVA) could be tailored by the reaction conditions such as the solvent composition, the concentration of initiator and the amount of monomer added. Finally, Chitosan-g-PVA hydrogels were formed by freezing-thawing cycles. The structure of graft copolymers was verified with FTIR. Both XRD analysis and contact angle test showed that the difference of crystallinity and hydrophilicity among chitosan, chitosan-g-PVAc and chitosan-g-PVA was evident. It was found that the maximum swelling ratios of chitosan-g-PVA hydrogels containing 37.6% and 46.2% PVA were 3.48 +/- 0.11 and 4.40. +/- 0.14 at pH 1.2, 1.90 +/- 0.13 and 2.80 +/- 0.15 at pH 7.4, respectively. This suggested the hydrogel was pH-sensitive, and its swelling behavior could be tailored with the graft percent of PVA. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2946-2950, 2010