Gas permeation and positron annihilation lifetime spectroscopy of poly(ether imides) containing main chain ethylene oxide segments

This article reports a study of four poly(ether imide)s with varying ethylene oxide (EO) segments lengths using positron annihilation lifetimes spectroscopy, wide angle X-ray diffraction, and gas transport measurements. The measured properties change with the length of the EO segment. Comparison of the poly(ether imide) containing a single ether linkage with those containing one and three EO units, show progressive changes of the permeability and diffusion coefficient with void size. However, when six EO units are incorporated into the polymer backbone certain of the observed trends are reversed. Incorporation of flexible EO segments in the polymer backbone allows changes in the chain-chain interactions which increases the packing density and changes the void size and influences the solubility coefficients leading to variation of the gas transport characteristics. Differences in the measured solubility parameters reflect the extent to which the gases molecules are able to interact with the polymer matrix. The highest values obtained for the gas separation for carbon dioxide and nitrogen is observed when EO has a value of three. Further increasing of the length of the EO segments in the poly(ether imide) leads to a reduction the gas transport properties and hence the extent to which gas separation would be achieved.