Promoting the separation efficiency of pervaporation membranes is a must to meet the growing demands of society. In this study, acetone-assisted interfacial polymerization was employed to produce thin-film composite (TFC) pervaporation membranes with improved performance. Two monomers were considered-diethylenetriamine (DETA) and trimesoyl chloride (TMC); they reacted with each other to form a thin polyamide layer, which was deposited on a hydrolyzed polyacrylonitrile (HPAN) substrate. Aqueous solutions containing different concentrations of acetone were used to dissolve DETA. Introducing acetone as a cosolvent of water enhanced the sorption of DETA in the HPAN support. It also altered and improved the physicochemical properties of the TFC membranes. An optimum concentration of 50 wt% aqueous acetone solution was established. Through acetone-assisted interfacial polymerization, a TFC membrane was then fabricated, and it exhibited a high separation efficiency: permeation flux = 1641 +/- 134 g.m(-2) h(-1) and water concentration in the permeate = 98%-99% (feed =70 wt% aqueous isopropanol solution). Moreover, the modified TFC membrane displayed a high separation performance at a wide range of operating conditions. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.