Structure-property relations for equilibrium swelling of cationic gels

Governing equations are developed for equilibrium swelling of a cationic polyelectrolyte gel in aqueous solutions with various pH and molar fractions of a monovalent salt. Material constants are determined by fitting observations on several homo- and copolymer gels in two types of tests: when swelling is conducted in water baths with varied pH and a fixed molar fraction of salt, and when experiments are performed in water baths with a fixed pH and varied concentration of salt. Phenomenological relations are suggested for the effect of total volume fraction of monomers in a pre-gel solution, molar fraction of ionic monomers, and molar fraction of cross-linker on adjustable parameters in the model.