Homogeneous membranes based on sulfonated cardo polyetherketone (SPEK-C) were prepared. The membranes were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), field emission high resolution transmission electron microscope (HRTEM) and contact angle meter. The results show that both the hydrophilicity and the amorphous region of the membranes increased with sulfortation degree (SD) increasing. The membranes show excellent thermal stability. Sulfonic acid groups exist as a form of ion clusters and distribute in the membranes homogeneously, which form the channel for permeants to pass through. The effects of solvent and SD on the performance of the membranes were studied. The results show that the SPEK-C membrane has excellent performance when the SID is 0.75 and dimethylsulfoxide is used as a solvent. Separation factor decreases and permeation flux increases with the feed temperature and water concentration increasing. The membrane has good separation performance with a flux of 248 g m(-2) h(-1) and separation factor of 103 at 50 degrees C in pervaporation of 90 wt% acetic acid in water. (c) 2007 Elsevier B.V. All rights reserved.