Preparation of asymmetric PEEKWC flat membranes with different microstructures by wet phase inversion

Membranes with controlled morphology were prepared by wet phase inversion from PEEKWC, a modified polyetheretherketone. Different membrane structures were obtained by using different nonsolvent/solvent pairs. The influence of several parameters, such as the composition of the polymer solution (concentration, type of solvent), the composition of the coagulation bath, and the exposure time before immersion in the coagulation bath, on the membrane morphology was Studied. The PEEKWC/solvent/nonsolvent phase diagrams, with various solvent/nonsolvent combinations, were determined and correlated to the process of phase separation during membrane formation. Using solvent/nonsolvent pairs with a high mutual affinity (DMF/water, DMA/water), porous membranes for possible application in microfiltration were obtained. The THF/water combination allowed the formation of asymmetric membranes with a dense skin layer, suitable for gas separation applications. Nitrogen permeance of all porous membranes was measured as function of pressure. Application of the Dusty Gas model permitted a qualitative description of the pore size and membrane morphology in relation to the membrane preparation conditions. (C) 2004 Wiley Periodicals, Inc.