Preparation and swelling behavior of amphoteric superabsorbent composite with semi-IPN composed of poly(acrylic acid)/Ca-bentonite/poly(dimethyldiallylammonium chloride)

Amphoteric superabsorbent composite with semi-interpenetrating polymer networks (semi-IPN) composed of poly(acrylic acid) (PAA)/Ca-bentonite/poly(dimethyldiallylammonium chloride) (PDMDAAC) was prepared by a combination of intercalative polymerization and a sequential IPN method and the effects of reaction parameters on the swelling capacity were studied. PDMDAAC was used as a polycation to modify bentonite and form semi-IPN with lightly crosslinked PAA. FTIR and TG were used to characterize the amphoteric superabsorbent composites with semi-IPN. The thermal stability of the product was not degraded as in the case of using small molecular surfactant to modify bentonite. The contents of carboxylic groups and nitrogen had been determined. This indicated that the product with certain content of carboxylic groups and nitrogen is inclined to exhibit excellent swelling capacity. The presence of PDMDAAC improved the swelling capacity. The resulting amphoteric superabsorbent composite showed excellent swelling capacity of 1578 g/g in distilled water and 136 g/g in 0.9 wt% NaCl solution. Copyright © 2007 John Wiley & Sons, Ltd.