Gas transport through homogeneous and asymmetric polyestercarbonate membranes

Permeabilities, solubilities and diffusivities of N₂, O₂, CO₂ and H₂ are reported for a polyestercarbonate at 35°C and 4.4 atm. Constant activation energies of permeation were determined for dense films and defect-free asymmetric polyestercarbonate membranes over a temperature range of 25-55°C. Activation energies of permeation were 10 and 20% higher for N₂ and O₂, respectively, in the asymmetric membrane samples as compared to the dense films. Permselectivities for the gas pairs O₂ N₂, H₂ N₂ and CO₂ N₂ were found to be higher in the asymmetric membranes compared to those of the dense films. The detailed cause of the higher permselectivities and activation energies in the asymmetric membranes is currently not known. Possible orientation-induced increases in segmental packing density in the asymmetric membrane skin is discussed as a potential explanation for the differences between the asymmetric and dense films.