ISOMER EFFECTS ON TRANSPORT-PROPERTIES OF POLYESTERS BASED ON BISPHENOL-A

Pure gas sorption and transport properties of polyesters based on bisphenol-A and both pure isophthalic and pure terephthalic acid chloride were obtained for He, N2, O2, CH4, and CO2 at 35-degrees-C. The polymers were synthesized in our laboratory and amorphous films were prepared with a specialized solvent casting procedure. The polymer containing m-phenylene groups shows higher permselectivity for most of the gas pairs. The ideal selectivity Of 02/N2 was increased by 33% when p-phenylene units were replaced by m-phenylene ones. On the other hand, the polyester containing only p-phenylene groups, shows higher permeability to all the gases studied. The polymer based on pure terephthalic acid chloride has a 75% higher oxygen permeability and a 1.1-fold higher carbon dioxide permeability than the isophthalic acid derivative. The polyester containing meta-phenylene units has lower T(g), higher permselectivity, lower permeability, lower fractional free volume (FFV), and lower d-spacing. The values of FFV and d-spacing were only slightly different between the two isomers. Moreover, for the sub-T(g) gamma transition the maximum in tan delta occurred at essentially the same temperature (55-degrees-C). The polymer with a higher concentration of p -phenylene units shows somewhat larger area under the gamma-peak, indicating slightly more sub-T(g), motion. The Distribution of FFV is considered to be the determining factor for the differences in transport properties observed. (C) 1993 John Wiley & Sons, Inc.