Nonporous polyvinyl alcohol (PVA) membrane was modified in gaseous plasma to improve the separation efficiency for water-isopropanol (IPA) mixtures. Method of pervaporation separation process was adopted to assess the permselectivity after plasma processing. Membranes were exposed to plasma of air, nitrogen and oxygen for 2-15 min, and, their performances was evaluated at 75degreesC for separation of azeotropic mixture of water-IPA. The optimized treatment time thus obtained for modification of PVA membrane was specifically used to further investigate the pervaporation performance over the selected water-IPA concentration range. Separation process at this stage was carried out at 25 and at 75degreesC. The modified membrane was characterized by ATR-FTIR spectrometry, thermal analyses using DSC and wide angle X-ray diffraction. It has been found that the nitrogen plasma processing induces cross-linking on membrane surface leading to effective improvement in separation performance of membrane. (C) 2004 Elsevier B.V. All rights reserved.