REDISTRIBUTION OF LOW-MOLECULAR-MASS ACID BETWEEN POLYELECTROLYTE HYDROGEL AND SOLUTION

The behavior of hydrogels based on polyacrylic acid with different deg ree of charging in hydrochloric acid solutions was studied. Redistribu tion of low-molecular-mass acid in the hydrogel-solution system and ch anges in the gel volume were examined. Depending on the ratio between the number of Na+ and H+ ions in the system, either bonding of hydroge n ions or an increase in acid concentration outside the hydrogel was o bserved. A simple model based on the Donnan theory, which took into ac count dissociation of carboxyl groups attached to the polymer network, provides a good description of experimental evidence.