• copolymers;
  • crystallization;
  • membranes


A vinyl amine–vinyl alcohol copolymer (VAm–VOH) was synthesized through free-radical polymerization, basic hydrolysis in methanol, acidic hydrolysis in water, and an anion-exchange process. In the copolymer, the primary amino groups on the VAm segment acted as the carrier for CO2-facilitated transport, and the vinyl alcohol segment was used to reduce the crystallinity and increase the gas permeance. VAm–VOH/polysulfone (PS) composite membranes for CO2 separation were prepared with the VAm–VOH copolymer as a selective layer and PS ultrafiltration membrane as a support. The membrane gas permselectivity was investigated with CO2, N2, and CH4 pure gases and their binary mixtures. The results show that the CO2 transport obeyed the facilitated transport mechanism, whereas N2 and CH4 followed the solution–diffusion mechanism. The increase in the VAm fraction in the copolymer resulted in a carrier content increase, a crystallinity increase, and intermolecular hydrogen-bond formation. Because of these factors, the CO2 permeance and CO2/N2 selectivity had maxima with the VAm fraction. At an optimum applied pressure of 0.14 MPa and at an optimum VAm fraction of 54.8%, the highest CO2 permeance of 189.4 GPU [1 GPU = 1 × 10−6 cm3(STP) cm−2 s−1 cmHg−1] and a CO2/N2 selectivity of 58.9 were obtained for the CO2/N2 mixture. The heat treatment was used to improve the CO2/N2 selectivity. At an applied pressure of 0.8–0.92 MPa, the membrane heat-treated under 100°C possessed a CO2 permeance of 82 GPU and a CO2/N2 selectivity of 60.4, whereas the non-heat-treated membrane exhibited a CO2 permeance of 111 GPU and a CO2/N2 selectivity of 45. After heat treatment, the CO2/N2 selectivity increased obviously, whereas the CO2 permeance decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40043.