Determination of average molecular weight between cross-links ( [formula omitted]) from swelling behaviours of diprotic acid-containing hydrogels

Abstract

Determination of average molecular weight between cross-links ( M c ) of itaconic acid-containing poly(vinyl pyrrolidone) and maleic acid-containing poly(acrylamide) hydrogels sensitive to pH changes of the swelling medium was investigated. Poly-electrolyte hydrogels with varying compositions were prepared in the form of rods from ternary mixtures of N-vinyl 2-pyrrolidone/itaconic acid/water and acrylamide/maleic acid/water. Gelation was achieved by irradiating the system with γ rays at ambient temperature. The equation modified by the authors recently for the determination of M c is observed to describe very well the swelling behaviour of charged polymeric networks. In addition to the evaluation of M c from swelling data, the same equation also provides the simultaneous measurement of polymer–solvent interaction parameter of the systems investigated.