Towards high-performance polysulfone membranes: A controllable membrane formation process using surfactant in NIPS

Increasing the molecular weight and addition contents of pore forming agents have been acknowledged as effective ways to improve permeability in membranes fabricated via nonsolvent induced phase separation (NIPS). However, these techniques negatively impact the overall pore size and mechanical strength of the resulting membranes. Facilitating the mutual diffusion of water (coagulant) and dope solutions (MDWDS) during NIPS is the key to obtain porous membranes with high permeability. Here, surfactants assisted nonsolvent induced phase separation (SA-NIPS) is proposed and used to regulate MDWDS during NIPS. Surfactants facilitate MDWDS. More importantly, MDWDS can be advanced by elevating the hydrophilic interaction force of water and the hydrophilic heads of surfactants while keeping the hydrophobic interaction in the dope solutions constant. SA-NIPS improves the surface porosity of polysulfone (PSF) membranes, thus increasing the permeability of PSF membranes (up to 2.9 times). Moreover, the tensile strength and pore sizes of PSF membranes are maintained. This research may provide a feasible insight into regulation of the morphology and permeability of NIPS-prepared membranes without compromising their pore size and tensile strength.