Construction of membrane formation system with low critical solution temperature for preparing hydrophilic polysulfone membrane via modified reverse thermally induced phase separation process

Abstract This paper presents a novel method to construct a membrane formation system featuring a low critical solution temperature (LCST) by incorporating hydroxy terminated hyperbranched polyester (HBPE) into polysulfone (PSF) casting solution. PSF membranes were developed by modified reverse thermally induced phase separation (m‐RTIPS) process while the introduction of HBPE improved the hydrophilicity of the membrane. The critical properties of the flat‐sheet PSF membranes were discussed in detail. The cloud point decreased as the HBPE concentration was increased. When membranes were prepared via m‐RTIPS, the region of bicontinuous finger‐like pores in the sublayer gradually broadened. The membranes showed better permeation properties, larger pore size, and better mechanical properties than those of the membranes prepared via non‐solvent‐induced phase separation (NIPS) process. Furthermore, no matter the enhanced hydrophilicity of membrane or m‐RTIPS membrane‐forming mechanism was beneficial to the anti‐fouling properties. In general, the membrane MPSF‐8‐b had relatively high flux, good hydrophilicity and excellent mechanical properties at 0.8 wt.% HBPE content, and the pure water flux recovery of the membrane was increased to 55.2%.