CHARACTERIZATION OF CO2-INDUCED CONDITIONING OF SUBSTITUTED POLYCARBONATES USING VARIOUS EXCHANGE PENETRANTS

A series of structurally-related polycarbonates are shown to retain a state of high permeability, induced by exposure to high pressure conditioning with CO2, even if the pure CO2 is completely replaced by CH4 or CO2/CH4 and O2/N2 mixed gas feed streams. Reductions, ranging from 0-15%, in the CO2/CH4 and O2/N2 separation factors occur for the substituted polycarbonates, while as much as a 30% enhancement in the flux of the various gases was observed. On the other hand, as was the case for standard polycarbonate, if the conditioning agent is completely replaced by helium, the conditioning treatment is not detectable, even after short times. The magnitude of the increase in permeability following an exchange experiment for a given penetrant, is qualitatively smaller for the substituted materials as compared to standard polycarbonate, because their less efficiently packed matrices experience smaller increases in fractional free volume. © 1990.