Sulfonated poly(phenylene oxide) (SPPO) membranes were prepared for dehydrating water/ethanol mixtures. The effects of hydration of sulfonated membranes on pervaporation (PV) performance were discussed by comparing the characteristics of pure PPO and SPPO membranes. The differences in microstructural and hydrophilic properties of membranes were characterized by means of atomic force microscopy and swelling test. The degree of sulfonation of PPO dominates the hydrophilicity of sulfonated membranes and it plays an important role to determine the dehydration performance of PV membranes. The sulfonated membranes present excellent water permeation rate of about 300 g m(-2) h(-1) with good selectivity up to 700. The experimental results also show that SPPO membranes exhibit better PV performance than pure PPO membranes due to the improvement in hydrophilicity of modified membranes with sulfonation method. The hydrophilic sulfonated membranes enhance the permeate hydration process in membrane matrix and increase the separation performance. (c) 2007 Wiley Periodicals, Inc.