Enhancement of CO2 permeability of poly(vinyl ether)s having oxyethylene chains by the sequence control of crosslinking sites

Sequential living cationic copolymerizations of vinyl ethers having oxyethylene side chains (MOEO 2 VE and MOEO3VE) with vinyl ether having a crosslinkable group (VEEM) provided the ABA-typed triblock copolymers poly(VEEM)-b-poly(MOEO2VE)-b-poly(VEEM) s and poly(VEEM)-b-poly(MOEO3VE)-b-poly(VEEM) s. All triblock copolymers are sticky liquids at room temperature, and the T(g)s were -77 to -73 degrees C. Heating the triblock copolymers afforded membranes by thermal crosslinking via mathacrylate groups at the outer segments in the polymers. All themembranes showed high CO2 permselectivity (P-CO2/P-N2 = 40-51) due to the high CO2 solubility selectivity (S-CO2/S-N2 = 44-61). The CO2 permeability of the triblock copolymers was higher than that of the random copolymers with the same composition ratios. This indicates that the inner segment (MOEO2VE and MOEO3VE) effectively enhanced the gas diffusivity in the polymer matrix because the crosslinking points are present only in the outer segments.