A UV/O-3 surface modification technology was used to develop high-performance dense polydimethylsiloxane (PDMS) pervaporation membranes for separating ethanol/water mixtures. Surface characteristics of PDMS membranes were evaluated by attenuated total reflectance - Fourier transform infrared spectroscopy, scanning electron microscopy - energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. The effect of UV/O-3 treatment time and working distance on the membrane physical and chemical properties and pervaporation performance were investigated. Results indicated that either longer treatment time or shorter working distance resulted in lower water contact angle and higher O/Si ratio, which implied higher conversion of PDMS into hydrophilic silica-like structure. The selectivity was greatly improved with longer treatment time and decreasing working distance. The UV/O-3 modification technique effectively increased the pervaporation performance of PDMS, especially at high temperature conditions of the feed. (c) 2012 Elsevier B.V. All rights reserved.