Soluble polyelectrolyte complex (PEC), made of poly(2-methacryloyloxy ethyl trimethylammonium chloride)/sodium carboxymethyl cellulose (PDMC/CMCNa), was modified by poly(vinyl alcohol) (PVA) with the content from 0 to 50 wt% to improve the PEC mechanical properties. It was found that the best mechanical properties of PEC/PVA blend containing 30 wt% PVA (PEC/PVA7030) were obtained. The tensile strength, modulus and elongation at break are about 1.5, 1.4 and 3.6 times of the pristine PEC. The prepared PEC/PVA blend membranes were subjected to the dehydration of 10 wt% water-isopropanol, displaying very good PV performance as the PVA content in PEC/PVA blend membranes is <= 30 wt%, especially for the selectivity of the PEC/PVA7030 blend membranes with and without polysulfone substrate, respectively. The results of the solution viscosity, differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic water contact angle (DWCA), equilibrium swelling degree (ESD) and field emission scanning electron microscopy (FESEM), and the mechanical behavior as well as pervaporation performance of PEC/PVA blends and their membranes all display special characters as the PEC/PVA blend contains 30 wt% PVA. These characters are interpreted in term of the compatibility of PEC and PVA. (C) 2011 Elsevier B.V. All rights reserved.