Design of urea-permeable anion-exchange membrane by radiation-induced graft polymerization

Abstract

Strong base anion-exchange membranes were prepared by radiation-induced graft polymerization. Quaternary ammonium salts were introduced onto nonporous polyethylene films by grafting of vinyl monomers such as glycidyl methacrylate (GMA), diethylaminoethyl methacrylate (DEAEMA), and vinyl benzyl trimethyl ammonium chloride (VBTAC), followed by subsequent chemical modifications. Hydroxyethyl methacrylate (HEMA) was cografted to (a) enhance the diffusion of the VBTAC into the polymeric matrix, and (b) initiate the grafting of the VBTAC. The VBTAC/HEMA-cografted membrane was selected because of its practical physical strength. Urea permeability across the resulting anion-exchange membrane was evaluated with a diffusion dialysis cell. Anion-exchange membranes with degrees of VBTAC/HEMA grafting higher than 70% exhibited urea and phosphate ion permeation. When the VBTAC/HEMA-cografted membrane was compared with a conventional anion-exchange membrane based on a styrene-divinylbenzene matrix, higher hydrophilicity and permeability were observed.