GAS SORPTION AND TRANSPORT-PROPERTIES OF BISPHENOL-I-POLYCARBONATE

Gas sorption and transport characterization of a new polymer in the po lycarbonate family, based on the bisphenol of 3,3,5-trimethylcyclohexa ne-1-one (BPI) is reported at 35-degrees-C. By comparison with propert ies of other known polycarbonates, the effects of inhibition of both p acking and segmental motion due to the introduction of the bulky subst ituent in the backbone are elucidated. The T(g) of the material was me asured with differential scanning calorimeter (DSC) and was found to b e unusually high for a polycarbonate (233-degrees-C). This indicates a successful inhibition of the large-scale segmental mobility of the po lymer. Vari-able C-13 NMR analysis indicated that rotation of one phen ylene ring has an unusually high (ca. 10 kcal) energy barrier, whereas the other phenylene ring has a more typical rotation profile (barrier < 3 kcal). The density was measured and found to be low (1.107 g/cm3) , indicating a high fractional free volume (FFV) for the polymer. Cons istent with expectations, the introduction of the bulky-substituted cy clohexane group gave high permeabilities for the various gases tested (N2, O2, He, CH4, CO2) compared to most standard polycarbonates. On th e other hand, the permselectivities were typical for standard polycarb onates. The solubility coefficients of all gases were rather high, as expected for a polymer with such an open structure. (C) 1994 John Wile y & Sons, Inc.