REACTION BETWEEN CHITOSAN AND CELLULOSE ON BIODEGRADABLE COMPOSITE FILM FORMATION

It was found that the film formation of composite films is accompanied by cross-linking between cellulose and chitosan, the composite films obtained thus becoming insoluble in water. In this paper the cross-linking reaction is discussed mainly from the point of view of biodegradability, swelling and strength of the composite film. An increase in the carboxyl groups of cellulose enhances cross-linkings in the composite film formation, while an increase in carboxyl groups does not. Though only trace amounts of carbonyl groups exist in cellulose, they evidently play an important role in cross-linking to chitosan. Further, the free amine form of the primary amino group of chitosan reacts more easily with cellulose than does the amine salt form. These facts suggest that one of the cross-linking structure between cellulose and chitosan in the stage of film formation originates from Schiff base formation between carbonyl groups of cellulose and primary amino groups of chitosan.