Abstract
Branched polyether was selected as a gas separation membrane with high CO2 permeability and good mechanical strength. Five branched-based copolymers with different number of oxyethylene unites in a side chain were considered as the best candidates. Molecular design was performed from the view point of crystallinity and molecular weight. The branched polyethers of ethylene oxide / side chain-containing monomer / allyl glycidyl ether by the dispersion polymerization method using the catalyst system of organic tin and phosphrous acid ester was carried out. All of the polyethers had high weight-averaged molecular weights over 105. From the result of thermal analysis, the polymers had glass transition temperature near - 70°C and the extremely low crystallinity. The branched polyethers displayed excellent performance for CO2/N2 separation, for example, CO2 permeability of 770 Barrer (1 Barrer= 10-10cm3(STP)cm cm -2 s -1cmHg -1) and CO2/N2 permselectivity of higher than 46 at 35°C. High permselectivity of these membranes were attributed to the solubility selectivity of the membrane due to the specific interaction between the polar nature of PEO and a high quadrupole moment of CO2. This result suggests that such branched polyethers may be a promising candidate for highly CO2 selective membrane material.
