Synthesis of amphoteric polymer membranes from epithiopropyl methacrylate–butylmethacrylate–N,N-dimethylaminopropyl acrylamide–methacrylic acid copolymers and the permeation behavior of various solutes through the membranes

Amphoteric polymers were prepared by copolymerization of epithiopropyl methacrylate (ETMA), butylmethacrylate (BMA), N,N-dimethylaminopropyl acrylamide (DMAPAA), and methacrylic acid (MAc) and the amphoteric polymer membranes were obtained by evaporation of solvent from its DMF solutions. And the diffusive permeability of solutes of LiCl, sodium benzenesulfonate (SBS), l-phenylalanine (l-phe), and styreneglycol (SG) through the amphoteric polymer membranes at various pHs and the change in the membrane potential during the permeation of the solutes through the amphoteric membranes were studied. The A1C2, A1C1, and A2C1 membranes having the ratio of 1/2, 1/1, and 2/1 of anion/cation-exchange capacity were selected for this study. The water content of the A1C2 and A2C1 membranes increased and decreased with increasing pH, respectively. The A1C1 membrane had the minimum water content at pH 7. The permeation of the solutes through the amphoteric polymer membranes was influenced by not only the swollen microporosity and the apparent charges of the amphoteric membranes but also the charge of the solutes at pH measured.