A series of polysulfone (PSf)-based amphiphilic graft copolymers were synthesized to investigate the effects of copolymer composition on membrane morphology and performance. PSf-based ultrafiltration membranes were prepared by phase inversion method using the blends of PSf and PSf-g-poly(ethylene glycol) methyl ether methacrylate (PEGMA) copolymers. Membranes were evaluated in terms of pure water permeability, flux recovery ratio (FRR), protein rejection, and contact angle. The morphology of the membranes was investigated by scanning electron microscopy. Contact angle of membranes was decreased from 85.7 degrees to 51.6 degrees, while the FRR was greatly increased from 55 to 95% upon increasing the PEGMA content of copolymers from 20 to 70 wt %. Results indicated that the ratio of hydrophilic/hydrophobic segments in amphiphilic structures is one the key parameters that control the phase inversion process by altering miscibility, viscosity, and wettability of casting solutions. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48306.