Equilibrium Swelling Studies of Chemically Cross-Linked Highly Swollen Acrylamide-Sodium Acrylate Hydrogels in Various Water-Solvent Mixtures

Swelling behavior of acrylamide (AAm)/sodium acrylate (SA) hydrogels was investigated in water-solvent (methanol, ethanol, t-butanol and acetone) mixtures of various compositions. AAm/SA hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with SA as comonomers and a multifunctional cross-linker such as trimethylolpropane triacrylate (TMPTA). Swelling experiments were performed in water and water-organic solvent mixtures of various compositions at 25°C, gravimetrically. The value of S_eq% of AAm/SA hydrogels are 64–152% for 60% of metanol, 84–102% for 60% of ethanol, 127–176% for 60% of t-butanol, 131–585% for 60% of acetone, while the value of S_eq% of AAm/SA hydrogels are 780–4510% for water and water-solvent mixtures. Some swelling kinetic parameters were found. Diffusion behavior of water and water-solvent mixtures was investigated. Diffusion of water and water-solvent mixtures into the hydrogels was found to be non-Fickian in character.