POLYSULFONE HOLLOW FIBER MEMBRANES SPUN FROM LEWIS ACID - BASE COMPLEXES .2. THE EFFECT OF LEWIS ACID TO BASE RATIO ON MEMBRANE-STRUCTURE

Oxygen plasma ablation has been used to define the structure of polysulfone hollow fiber membranes spun from Lewis acid:base complex solvents in which the molar ratio of propionic acid to N‐methylpyrrolidone was varied. It was found that the helium/nitrogen separation factor of the unetched samples increases with increasing PA/NMP molar ratios. This increase implies a decrease in surface porosity of the resultant hollow fiber as larger fractions of the total NMP in the solvent are complexed with propionic acid. The results also suggest that the differences between the outer separating layer and the supporting matrix increase with increases in the PA/NMP molar ratios. Therefore, a more rapid transition from the separating layer to the porous supporting matrix exists in hollow fiber membranes spun from the higher PA/NMP ratios. Copyright © 1990 John Wiley & Sons, Inc.