Membranes based on sulfonated polyarylethersulfone with cardo (SPES-C) were prepared and characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and contact angle metering. The results show that both the hydrophilicity and amorphous region of the membranes increased with increasing sulfonation degree (SD). Sulfonic acid groups exist as a form of ion clusters and homogeneously distribute in the membranes leading to a depression in their crystallinity and an increase in the interaction between methanol and the membranes. The effects of SD on the swelling and separation performance of the membranes were studied. The SPES-C membrane with excellent thermal stability is found to have improved performance when the SD is 0.64. A flux of 4.06 kg mu m m(-2) h(-1) and separation factor of 1300 at 40 degrees C are achieved in pervaporation of 15 wt% methanol/methyl tert-butyl ether mixture. (C) 2012 Elsevier B.V. All rights reserved.