Several copolymers of acrylonitrile (AN) were synthesized. Methanol selective membranes were prepared from these copolymers of AN. The other monomers in the copolymers were selected on the basis of their solubility parameter values relative to those of methanol. These were hydroxyethyl methacrylate, methacrylic acid, and vinyl pyrrolidone. Thus, pervaporative separation of methanol from its mixture with methyl tertiary butyl ether over the entire concentration range of 0-100% methanol was studied using these copolymer membranes of AN. For each copolymer of AN three different membranes with different copolymer compositions were prepared. Copolymers of AN with hydroxyethyl methacrylate and methacrylic acid showed high selectivity and moderate flux for methanol (2561, 773, 0.057, and 0.045 kg/m(2) h, respectively, with a membrane of 50-mu m thickness for a feed mixture containing 5% methanol at 30 degrees C). A copolymer of AN with vinyl pyrrolidone showed comparable flux, but methanol selectivity of this membrane was poor.