A new and useful form of phase inversion for the formation of porous polymeric membranes is presented herein. As in the case of thermally induced phase separation (TIPS), this new form involves only two components (polymer and solvent) and a thermal quench; here the quench is accomplished via immersion in a cold bath of the micromolecular component (solvent) of the dope. Ιn terms of a fixed-pressure two-component phase diagram the quench is a non-vertical one. We will refer to the new method as cold-solvent induced phase separation (CIPS). In the present work we study mainly the poly(ethylene-co-vinyl alcohol)/1,3-propanediol system which leads to bi-continuous structures stemming from a combination of liquid-liquid demixing and crystallization. In addition, we compare with the case of the Nylon-l2/formic acid system that we have briefly considered before and study further herein; the consequences of the TIPS to CIPS shift of method are different for the two systems, and the two situations are representative of two general possibilities. We also report general properties such as porosity, tensile strength, water permeation flux, and crystallinity of the produced poly(ethylene-co-vinyl alcohol) membranes.
