Swelling Behavior of Polyacrylamide Hydrogels near Phase Transition

Abstract

Hydrogels based on acrylamide (AA) and sodium methacrylate (NMA) as ionic monomer were prepared by solution polymerization using N,N’-methylenebis(acrylamide) (MBA) or ethylene glycol dimethacrylate (EGMA) as crosslinkers and Ammonium Persulfate (APS) and N,N,N’,N’-Te-tramethyl-ethylenediamine (TMEDA) as initiators. Swelling behavior was greatly affected by NMA content near phase transition. Increasing ionic monomer concentration compared to total monomer one led to high expansion in water, oscillating around 285 g/g for MBA and 325 g/g for EGMA crosslinker, above 20% of NMA. Dynamic Light Scattering experiments were performed and, for both crosslinkers, the dynamic correlation length ( ξ ) decreased with increasing NMA content, contributing to diminish hydrogels spatial inhomogeneities.