Swelling behaviors of polyelectrolyte hydrogels containing sulfonate groups

Series of maleate monoester and diester monomers based on poly(ethylene glycol) monomethyl ether (MPEG) were copolymerized using the ionizable 2‐acrylamido‐2–methyl propane sulfonic acid (AMPS) via different dose rate of electron‐beam irradiation (40–150 kGy). The crosslinking of the copolymers were carried out in aqueous acidic solutions at pH 1 or in the presence of 1% N,N‐methylene bisacrylamide (MBA) as crosslinking agent. The final equilibrium water content and swelling capacities for the prepared hydrogels were determined in aqueous solutions at pH 1, 6.8, and 12 and in aqueous salt solutions at 298 K. Swelling equilibria for prepared hydrogels were determined in different molar salt solutions of NaCl, KCl, CaCl₂, Na₂SO₄, K₂SO₄, and CaSO₄. The swelling ratios of gels in pure water and in the salt solutions were found to depend on the counterion species in the increasing sequence of Ca²⁺, Na⁺ and K⁺. Copyright © 2002 John Wiley & Sons, Ltd.