The effects of hydrophilic monomers e.g. acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) on the morphology and performance of polyethersulfone (PES) membrane were investigated. The membranes were fabricated from a casting solution of PES, dimethylacetamide (DMAC), polyvinylpyrrolidone (PVP) and AA or HEMA via phase inversion induced by immersion precipitation. The mixture of water (80 vol.%) and 2-propanole (IPA, 20 vol.%) was employed as gelation media. The prepared membranes were characterized using ATR-FTIR, SEM, AFM, contact angle, viscosity measurements, ultrafiltration performance and fouling analysis. The hydrophilicity of PES membrane was improved after addition of AA and HEMA in the casting solution. The morphological studies (SEM and AFM) showed that the average sizes of membrane pores in surface and sub-layer were reduced with addition of AA and HEMA in the casting solution. Meanwhile the surface porosity was increased. The surface pore size of the untreated PES membrane was decreased from 138 nm to 45.1 and 40.6 nm with introducing 15 wt.% AA and HEMA, respectively. The experimental results showed that the pure water fluxes of membranes were declined at the presence of AA and HEMA. Moreover, the milk water permeation and protein rejection were improved at these conditions. Finally, the fouling analysis demonstrated that the membranes show fewer tendencies for fouling. (C) 2010 Elsevier B.V. All rights reserved.