A water-soluble copolymeric membrane material containing tertiary amine and carboxyl groups for CO2 facilitated transport have been synthesized by radical polymerization of DMAEMA (2-N,N-dimethyl aminoethyl methacrylate)-AA (acrylic acid). The composite membranes were prepared with copolymer of DMAEMA-AA as separation layer and polysulfone (PS) ultra-filtration membrane as support. The permeation rates of the membranes for pure CO2 and CH4 were investigated. The results show that the copolymeric membrane possesses a higher permeance of CO2. The membrane displays a CO2 permeance of 6.12 x 10(-7) cm(3) (STP)/cm(2) s Pa, and a CH4 permeance of 2.4 x 10(-9) cm(3) (STP)/cm(2) s Pa at 299 K, 1.140 kPa of gas pressure. The results with the mixed gas are not as good as those obtained with pure gas because of the coupling effects between CO2 and CH4. (c) 2006 Elsevier B.V. All rights reserved.