Pure and Mixed-Gas Permeation Study Of Thermally Rearranged Polymers

Results of pure and mixed-gas permeation in thermally rearranged polymers are presented.  Polyimide precursor films were converted to their polybenzoxazole (PBO) analogs to varying degrees using different thermal treatment protocols.  Structure/property relations in this family of polymers are described.  Mixed-gas permeation results are compared against pure-gas measurements.  Interestingly, CO₂/CH₄ mixed-gas selectivity at 35°C was 20-30% higher than the simple ratio of pure-gas permeabilities.  Strong dual-mode effects were responsible for a decrease in CH₄ permeability in the presence of CO₂, with very little change to CO₂ permeability in the mixture.  Plasticization is not evident in the pure-gas CO₂ permeation data.