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

Abstract

Sequential living cationic copolymerizations of vinyl ethers having oxyethylene side chains (MOEO₂VE 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_gs were −77 to −73 °C. Heating the triblock copolymers afforded membranes by thermal crosslinking via mathacrylate groups at the outer segments in the polymers. All the membranes 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.