Study on Preparation of Microporous Membrane via PES Low Critical Solution Temperature System

Microporous polyethersulfone(PES) membranes were successfully prepared by thermally induced phase separation method in which the employed membrane-forming system features a low critical solution temperature(LCST-TIPS,i.e.RTIPS) and consists of PES,N,N-dimethylacetamide(DMAc) and diethylene glycol(DEG).Light transmittance was performed to survey the LCST during the RTIPS process.The morphology and performance of the prepared PES membranes were respectively characterized with scanning electron microscopy,permeation and mechanical experiments.The effects of the mass ratios of nonsolvent/solvent(DEG:DMAc) and water bath temperature on membrane structure and properties were investigated.The results show that the phase separation temperature decreases with increasing mass ratio of DEG:DMAc.Using the RTIPS process,the membrane structure changes from a finger-like pores structure to a bicontinuous structure along its cross-section,and a porous surface was also observed.With the mass ratio of DEG:DMAc of 0.8:1 and the water bath temperature of 60℃,the membrane has the maximum mean pore size and pure water flux.Moreover,the mechanical properties of membranes prepared via the RTIPS are better than those of the membranes prepared by nonsolvent induced phase separation(NIPS) method.