Preparation of vinyl amine-co-vinyl alcohol/polysulfone composite membranes and their carbon dioxide facilitated transport properties

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 CO 2 -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 CO 2 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 CO 2 , N 2 , and CH 4 pure gases and their binary mixtures. The results show that the CO 2 transport obeyed the facilitated transport mechanism, whereas N 2 and CH 4 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 CO 2 permeance and CO 2 /N 2 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 CO 2 permeance of 189.4 GPU [1 GPU = 1 × 10 −6 cm 3 (STP) cm −2 s −1 cmHg −1 ] and a CO 2 /N 2 selectivity of 58.9 were obtained for the CO 2 /N 2 mixture. The heat treatment was used to improve the CO 2 /N 2 selectivity. At an applied pressure of 0.8–0.92 MPa, the membrane heat-treated under 100°C possessed a CO 2 permeance of 82 GPU and a CO 2 /N 2 selectivity of 60.4, whereas the non-heat-treated membrane exhibited a CO 2 permeance of 111 GPU and a CO 2 /N 2 selectivity of 45. After heat treatment, the CO 2 /N 2 selectivity increased obviously, whereas the CO 2 permeance decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131 , 40043.