This article presents the systematic study of kinetics and mechanism of phase-transfer-catalyzed free-radical polymerization of acrylonitrile (AN) and water-soluble initiator potassium peroxomonosulphate (PMS) coupled with tetrabutyl phosphonium chloride (TBPC) in ethyl acetate/water biphase system in the temperature range 45-55 degrees C at fixed pH and ionic strength. The rate of polymerization increases with an increase in concentrations of AN, PMS, and phase transfer catalyst, PTC. It was observed that R-p is proportional to [AN](1.5), [KHSO5(5)(-)](0.5), and [TBPC](0.5). A suitable kinetic scheme has been proposed to account for the experimental observations and its significance was discussed. (C) 2000 John Wiley & Sons, Inc.