Gas transport properties of 6FDA‐durene/1,3‐phenylenediamine (mPDA) copolyimides

The gas transport properties of He, H 2 , O 2 , N 2 , and CO 2 for 6FDA‐durene, 6FDA‐mPDA, and their copolyimides have been investigated as a function of the composition, pressure, and temperature. The permeabilities, diffusion coefficients, and solubility coefficients follow the simple additional rules and Arrihenuis relationships for 6FDA‐durene/mPDA polyimides. The permeability decreases with an increase in pressure except He, and in the kinetic diameters of the penetrant molecules with the order of He, CO 2 , O 2 , and N 2 . The diffusion coefficients of O 2 , N 2 , and CO 2 increase with increasing pressure and temperature. Interestingly, for these polyimides, the diffusion coefficient of O 2 is larger than that of CO 2 . This may be caused by the strong quadrupole moment of the CO 2 molecules or the difficulty in estimating the accurate diameter of CO 2 molecules. The solubility coefficients decrease in the order of inherent condensability of the penetrant gases, namely CO 2 , O 2 , and N 2 . In addition, WAXD results show that 6FDA‐durene/mPDA polyimides are amorphous. The presence of a single glass transition temperature for these copolyimides indicates that these polyimides can be assumed to be random copolymers. They have excellent thermal stability exhibiting degradation temperature in a range of 493 to 548°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3552–3564, 2001