Transport properties of poly(ether imides)

Gas-separation membrane properties of new poly(ether imides) with a common diamine fragment were studied, and permeability and diffusion coefficients for gases, such as H-2, He, O-2, N-2, CO2, and CH4, were determined. For a series of the allied polymers, the selectivity of gas separation was significantly affected by a small change in the free volume. One of the tested poly(ether imides) that was prepared through the polycondensation of 2,2-bis [(4-3,4'-dicarboxyphenoxy)phenyl]propane and 1,1,1,3,3,3-hexafluoro-2,2-bis[(3-aminophenoxy)-p-phenylene]propane, poly(ether imide) VI, holds promise as a gas-separation material. Due to the high selectivity of gas solubility, poly(ether imide) VI turned out to be above the upper bound on the Robeson diagram. The transport parameters of the related poly(ether imides) with a common dianhydride fragment were also examined. It was demonstrated that all the polymers of interest rank below poly(ether imide) VI in gas-separation selectivity. The group contribution method was used to predict the permeability coefficients for all the examined poly(ether imides), and the predicted transport parameters were found to correlate well with the experimental values.