Gas diffusion and solubility in He+-irradiated asymmetric polyimide membranes

In this study, the gas diffusion and solubility of the asymmetric polyimide membrane irradiated by He ions were investigated using a high vacuum apparatus equipped with a Baratron absolute pressure gauge at 76 cmHg and 35 °C. Specifically, we estimated their effects on the gas permeation properties of the asymmetric membranes. The asymmetric polyimide membranes were prepared by a dry–wet phase inversion process, and the surface skin layer on the membrane was irradiated by He ions at fluences of 1 × 1015 or 3 × 1015 ions/cm2 at 150 keV. We demonstrated that the gas diffusion had a significant influence on the gas permeability and selectivity of the He+-irradiated asymmetric membrane.