Gas sorption and permeation in PIM-1

Gas transport properties of PIM-1, i.e., the first "polymer with intrinsic microporosity," at 25°C and different pressures were systematically studied. Permeability coefficients of 10 gases including He, H₂, N₂, O₂, CH₄, CO₂, C₂H₄, C₂H₆, C₃H₆ and C₃H₈ were conducted at 25°C for five different upstream pressures (from 1 to 10atm). The C₂ and C₃ hydrocarbons exhibited serious plasticization responses while the permeability coefficients of He, H₂, O₂, N₂, CH₄ and CO₂ decreased with the trans-membrane pressure as expected from the dual-mobility model. Sorption isotherms of all 10 gases were also determined using a dual-volume sorption cell at 25°C up to a maximum pressure of 27atm. The sorption isotherms followed the dual-mode sorption model. The logarithm of the solubility coefficients increased linearly with the critical temperature of the gas and the slope of this plot (0.018) was found to be comparable with values reported for other glassy polymers. Diffusion coefficients were calculated from the permeability and solubility data; the values for He, H₂, O₂, N₂, CH₄ and CO₂, increased with pressure as predicted by the dual-mobility model while those of the C₂ and C₃ hydrocarbon gases increased more strongly because of plasticization. Parameters from the dual mobility model, D_D and D_H, were significantly higher and their ratio, D_H/D_D was significantly smaller than those of previously reported polymers.