Determination of average molecular weight between crosslinks and polymer–solvent interaction parameters of poly(acrylamide‐ g ‐ethylene diamine tetraacetic acid) polyelectrolyte hydrogels

Hydrogels containing tetraprotic acid moieties sensitive to pH changes of the swelling medium were prepared from the ternary systems acrylamide/ethylene diamine tetraacetic acid/water by irradiation with γ‐rays at ambient temperature. Gel compositions of poly(acrylamide‐ g ‐ethylene diamine tetraacetic acid) [P(AAm‐ g ‐EDTA)] hydrogels were determined by using a differential pulse polarography technique. Equilibrium swelling behavior of these hydrogels was studied using an equation, based on the Flory–Huggins thermodynamic theory, the phantom network theory of James–Guth, and the approaches of Brannon‐Peppas and Peppas, which was modified by the authors for determination of M c and χ parameters. The equation modified by the authors for the determination of M c and χ parameters were observed to describe very well the swelling behavior of the charged polymeric network.