SWELLING PROPERTIES OF ACRYLAMIDE-BASED AMPHOLYTIC HYDROGELS - COMPARISON OF EXPERIMENT WITH THEORY

Ampholytic hydrogels were synthesized by copolymerizing acrylamide wit h specialty monomers. Two monomers, [(methacrylamido)propyl]trimethyla mmonium chloride (MAPTAC) and sodium styrene sulfonate (SSS), were cop olymerized with acrylamide to form one ampholytic hydrogel. Also, the zwitterionic monomers ropyl)-N-methacrylamidopropyl-N,N-dimethylammoni um betaine (SB1) and opropyl)-N-methacroyloxyethyl-N,N-dimethylammoniu m betaine betaine (SB2) were both, in turn, copolymerized with acrylam ide to form ampholytic hydrogels. Swelling equilibria were measured in water and in aqueous sodium chloride solutions ranging in concentrati on from 10(-5) to 5 M. Antipolyelectrolyte behaviour was observed for the ampholytic hydrogels prepared, hydrogel swelling increases as the sodium chloride concentration rises. To demonstrate theoretically anti polyelectrolyte behaviour for ampholytic hydrogels, we incorporate the Debye-Huckel theory of electrolyte solutions into a Flory-type swelli ng model to account for Coulombic interactions between fixed and mobil e ions. Calculated swelling equilibria are in qualitative agreement wi th experiment.