In this study, a novel and environmentally friendly extracting method, supercritical carbon dioxide (SC-CO2) extraction, was investigated in the thermally induced phase separation (TIPS) process for making microporous membranes. In the SC-CO2 extraction, the effects of extraction time, pressure, and temperature on the extraction fraction, membrane morphology, and membrane performance were investigated. It was concluded that with extraction conditions of 18 MPa, 35 degrees C and 2 h, the porous membrane had the highest extraction fraction. There was a close relationship between membrane performance and the extraction conditions of SC-CO2, and it is possible to tailor membrane performance through the choice of extraction conditions. Compared with traditional solvent extraction, a dry membrane treated by SC-CO2 extraction has much less shrinkage and greater water permeability, whereas the degree of crystallization of a membrane extracted by SC-CO2 is slightly greater than that extracted by ethanol. (c) 2006 Wiley Periodicals, Inc.