We fabricated a novel high-performance pervaporation membrane for ethanol dehydration through interfacial polymerization integrated with spin-coating, a method we called dynamic interfacial polymerization. Varying amine and ac-yl chloride monomers were used to assemble heterogeneous polyamicle layers on an electrospun polyacrylonitrile substrate. The performance of the composite membrane comprising a highly crosslinked top layer surpassed that of the commercial PERVAP 2210 membrane: the permeation flux (13.9 kg/m(2)h) was eight Limes higher and the separation factor (4491) 19 Limes. It also exhibited stability during the peryaporation operation for 20 clays. Positron annihilation lifetime spectroscopy indicated the effect of the layers' free volume on the membrane performance. Doppler broadening energy spectroscopy gave information on interfacial defects. We also investigated the performance of composite membranes with homogeneous layers; despite assembling five homogeneous layers, the permeate concentration reached only up to 93.7 wt% water. (C) 2014 Elsevier B.V. All rights reserved.