Ultrathin Multicomponent Poly(ether sulfone) Membranes for Gas Separation Made by Dry/Wet Phase Inversion

Asymmetric gas separation membranes were prepared by a dry/wet phase inversion process using poly(ether sulfone) as membrane-forming material. Variations in the composition of multicomponent casting solutions and choice of the coagulation medium resulted in membranes with drastically different gas separation properties. Optimized integral-asymmetric poly(ether sulfone) membranes coagulated in methanol had pressure-normalized CO₂fluxes of 7.2 x 10^-5cm³(STP)/ (cm²•s•cmHg) and a CO₂/N₂selectivity of 40. However, asymmetric membranes coated with a thin layer of silicone rubber showed substantially improved gas separation performance. Poly(ether sulfone)/silicone multicomponent membranes showed pressure-normalized CO₂fluxes of up to 6.2 X 10^-5cm³(STP)/(cm²•s•cmHg) combined with a CO₂/N₂selectivity of 60, essentially equal to the intrinsic permselectivity of poly (ether sulfone). The estimated, effective skin thickness of these membranes is on the order of 500 Å. Pressure-normalized fluxes of poly(ether sulfone) membranes made by dry/wet phase inversion are equal to or higher than those of graded density skin membranes made by a traditional wet phase inversion process using Lewis acid-Lewis base complex solvent systems.