A new type of surface modifying macromolecule (nSMM) was designed and synthesized to incorporate polydimethylsiloxane (PDMS) component in its structure. Gel permeation chromatography (GPC) and elemental analysis were used to characterize the synthesized nSMM. Also nSMM blended polyethersulfone (PES) membranes were prepared with different compositions, evaporation temperature and evaporation period. Prepared membranes were characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and pure water permeation (PWP) test. According to the results, nSMM migrated to the surface and effectively increased the surface hydrophobicity of PES membranes when blended. Increase in liquid entry pressure of water (LEPw) with an increase of surface contact angle was also observed. (c) 2005 Elsevier B.V. All rights reserved.