The mechanism of shrinkage and dehydration of ionic hydrogels packed in an electric cell were investigated on the basis of the distribution of pH around the gel, the Na⁺ ion concentration within the gels packed in the cell and the dehydration rate.
It was found that shrinkage and dehydration of the ionic gels take place through the following processes : (1) generation of H⁺ and OH^- ions by electrolysis ; (2) ion-exchange between H⁺ ions generated on the anode and Na⁺ ions dissociated originally within the gels ; (3) accumulation of Na⁺ ions near the cathode by electrophoresis ; and (4) increasein ionic strength near the cathode caused by process (3). Therefore, the shrinkage and dehydration of ionic gels depend on the generation of H⁺ ions by electrolysis and electrophoresis of Na⁺ ions.