Swelling and collapse of the gel composites based on neutral and slightly charged poly(acrylamide) gels containing Na-montmorillonite

Clay-polymer hydrogel composites were prepared on the basis of neutral and slightly charged cationic and anionic poly(acrylamide) gels containing different amounts of the clay mineral Na-montmorillonite. The swelling and collapse in water-acetone media and the mechanical behavior of such gels were studied. It is shown that the clay incorporated into neutral poly(acrylamide) gel hardly influences its degree of swelling in water. On the other hand, for the anionic and especially for the cationic gels, the swelling in the presence of clay decreases. The elastic modulus of gels with incorporated clay is higher, while the amplitude of the acetone-induced collapse is lower than for the corresponding pure gel systems. (C) 1998 Elsevier Science Ltd. All rights reserved.