Polysulfone (PSF) is extensively used for the production of ultrafiltration (UF) membranes thanks to its high strength

chemical stability

and good processibility. However

PSF is intrinsically hydrophobic

and hydrophilic modification is always required to PSF-based membranes if they are intended to be used in aqueous systems. Facile strategies to prepare hydrophilic PSF membranes are thus highly demanded. Herein we spray coat a PSF-based amphiphilic block polymer onto macroporous substrates followed by selective swelling to prepare flat-sheet PSF UF membranes. The polymer is a triblock polymer containing PSF as the majority middle block tethered with shorter block of polyethylene glycol (PEG) on both ends

that is

PEG-

b

-PSF-

b

-PEG. We use the technique of spray coating to homogeneously dispense diluted triblock polymer solutions on the top of macroporous supports

instantly resulting in uniform

defect-free polymer coating layers with the thickness down to ~1.2 μm. The bi-layered composite structures are then immerged in ethanol/acetone mixture to generate mesoscale pores in the coating layers following the mech

anism of selective swelling-induced pore generation

thus producing composite membranes with the mesoporous triblock polymer coating as the selective layers. This facile strategy is free from additional hydrophilic modification and much smaller dosages of polymers are used compared to conventional casting methods. The pore sizes

porosities

hydrophilicity

and consequently the separation properties of the membranes can be flexibly tuned by changing the swelling duration and the composition of the swelling bath. This strategy combining spray coating and selective swelling is upscalable for the production of high-performance PSF UF membranes.