Study of carboxymethyl chitosan based polyampholyte superabsorbent polymer I: Optimization of synthesis conditions and pH sensitive property study of carboxymethyl chitosan-g-poly(acrylic acid-co-dimethyldiallylammonium chloride) superabsorbent polymer

A novel polyampholyte superabsorbent polymer-carboxymethyl chitosan-g-poly(acrylic acid-co-dimethyldiallylammonium chloride) (CMCTS-g-(PAA-co-PDMDAAC)) has been prepared through the graft copolymerization of acrylic acid (AA) and dimethyldiallylammonium chloride (DMDAAC) onto the chain of carboxymethyl chitosan. The optimal conditions for synthesizing the polymer with the highest swelling ratio has been identified by studying the water absorption of the polymer prepared under different conditions. The swelling ratio of the prepared polyampholytic polymer was found to be pH dependent, and in particular, the prepared polymer showed peaks in swelling capacity at both acidic condition (pH 3.5) and basic condition (pH 9.5). The effects of the interactions between the charged groups on the polymer backbone as well as the counter ion screening on the non-freezable water content have also been studied by measuring the DSC curve of the swollen hydrogel at different pH values.