Morphology control of asymmetric membranes by UV irradiation on polyimide dope solution

The membrane morphology was readily controlled by the gelation of dope solu tion before immersion into a coagulation medium. In particular, macrovoid-f ree, sponge-like integrally skinned asymmetric polyimide membranes with imp roved selectivity were obtained by the chemical gelation of cast solution f ilm. Cross-linking was performed by ultraviolet irradiation for benzophenon e containing polyimide dope solution. Cross-linking maintained the structur e of cast solution him until the moment of immersion into a nonsolvent bath . Macrovoid decreases with irradiation time on the cast solution Blm. Spong e-like integrally skinned asymmetric membranes were obtained with sufficien t irradiation. Gas permselectivity increased significantly with the progres s of cross-linking on the cast solution him. Membrane morphology and subseq uent transport properties can be controlled both by the extent of cross-lin king and by the concentration of dope solution, (C) 2000 Elsevier Science B .V. All rights reserved.