Cross-linked poly (vinyl alcohol) membranes were prepared using fumaric acid as the cross-linking agent and were used for the pervaporation separation of water/isopropanol mixtures. Cross-linking process was carried out at 150 degrees C at three different times of 10, 30, and 60 min. The membranes were characterized by different known methods of FT-IR, TGA, XRD as well as tensile test. The effects of cross-linking time on the thermal and mechanical properties of the membranes and also their pervaporation performance were investigated. Formation of more ester groups by increasing the cross-linking time was confirmed by the FT-IR results. TGA analyses showed that thermal stability of the membranes is improved by prolonging the duration of cross-linking process. This was due to the formation of more compact structure in the membranes. The XRD results revealed that the crystalline regions of the membranes were relatively diminished with an increase in the cross-linking time. No specific trend was observed for the variation of tensile strength at break with the cross-linking time. The PVA membrane cross-linked for 60 min showed high selectivity of 1492 for water permeation for the feed mixture containing 10 wt % water. The temperature dependency of the permeation flux was investigated using Arrhenius relationship, and the activation energy values were calculated for total permeation (Ep), water (Epw), and IPA (EpIPA) fluxes. Lower value of Epw in comparison with EpIPA supported excellent dehydration performance of the cross-linked membranes. Despite large increase in activation energy of water with prolonged cross-linking time, the selectivity was improved. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2013