Isomer effects on transport properties of polyesters based on bisphenol‐A

Abstract

AbstractPure 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°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 O2/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 Tg, higher permselectivity, lower permeability, lower fractional free volume (FFV), and lower d‐spacing. The values of FFV, and lower d‐spacing. The values of FFV and d‐spacing were only slightly different between the two isomers. Moreover, for the sub‐Tgγ transition the maximum in tan δ occured at essentially the same temperature (−55°C). The polymer with a higher concentration of p‐phenylene units shows somewhat larger area under the γ‐peak, indicating slightly more sub‐Tg motion. The Distribution of FFV is considered to be the determining factor for the differences in transport properties observed. © 1993 John Wiley & Sons, Inc.