Recent advances in preparation and morphology control of polymeric membranes formed by nonsolvent induced phase separation

Nonsolvent induced phase separation (NIPS) is the most widely used method to prepare membranes for separation processes. Even though it has been used for about five decades, NIPS still attracts much attention nowadays. In the present article, we first discuss some recent advances in the fundamentals of NIPS, including the mechanism of membrane formation and the selection of polymer, solvent, and nonsolvent. We will also review the recent researches about modification of membranes by blending copolymers or inorganic particles in the casting solution. The blending modification technique has drawn extensive attention because it can accomplish membrane fabrication and modification in one step. In addition, reviews are given for the development of three novel morphology control techniques based on NIPS: phase separation micromolding (a method combining lithography and NIPS), the 'breath figure' method (a phase separation process induced by water vapor), and a technique based on the combination of NIPS and self-assembly of block copolymers.