Swelling-induced structure changes of polyelectrolyte gels

The structural changes of hydrophilic polymer networks were studied by SANS . The size of heterogeneities in the network was measured for gels swollen in different amount of water. The type of cross-linking agent, degree of cr oss-linking and degree of ionisation were varied. The dependence of the siz e of heterogeneities on the degree of swelling shows a great difference for gels which exhibit strong polyelectrolyte properties (can swell hundreds o f times) comparing with the ones which can swell less than 100 g/g. The int erpretation of the observed phenomenon is based on the appearance of strong electrostatic interactions which are dominating in the gel-swelling mechan ism at high degree of swelling. (C) 1999 Elsevier Science Ltd. All rights r eserved.