Hourglass-like structure tailoring of PES-b-PEG microfiltration membranes via varying humid air bath time

A novel high-flux polyethersulfone- block -polyethylene glycol (PES- b -PEG) microfiltration (MF) membrane was developed via the vapor-assisted non-solvent-induced phase separation (V-NIPS) method using a 10-s humid air bath. Compared to control PES membranes, the PES- b -PEG membranes exhibit a looser, hourglass-like structure with higher porosity, larger pore diameters, and enhanced water flux and filtration capacity. The onset position of the hourglass-like pores can be finely tuned by adjusting the humid air bath time, enabling significant control over pore diameter and water permeance. Incorporation of PEG into the block copolymer, along with the low viscosity of the casting solution, accelerates water uptake and improves compatibility with water during V-NIPS, promoting efficient vapor-induced phase separation (VIPS) and the formation of a looser, highly permeable structure. With a 10-s air bath, the PES- b -PEG membrane achieves water flux of 45,712 L m −2  h −1 bar −1 , a pore diameter of 0.8 μm, 99.5 % rejection of 1.0 μm polystyrene microspheres, and a filtration capacity of 1,233 L m −2 (at 10 % flux decline). This study highlights the advantages of PES- b -PEG block copolymers for producing high-performance MF membranes with a tailorable hourglass-like architecture via ultrashort humid air exposure.