Poly(benz-3,1-oxazinone-4) was prepared by thermal cyclization of its hydrolytically stable precursor polyamic acid. Both polymer and its precursor were investigated as membrane materials. Thermogravimetric analysis and contact angle measurements were carried out for characterization of peculiarity of membrane compositions and analysis of membrane surface. Pervaporation of water-isopropanol mixture was studied in the wide range of feed composition. To interpret the pervaporation transport properties of the membranes, swelling experiments were performed, kinetic curves of sorption and desorption were plotted, and basic sorption and diffusion parameters were analyzed. It was established that poly(benz-3,1-oxazinone-4) membrane is extremely effective in dehydration of water-isopropanol mixture and shows high separation factor. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4024-4031, 2013