In this study, polyamide (PA) composite membranes (DMDPA-TMC/CA, NTEA-TMC/CA, DETA-TMC/CA) were prepared through the interfacial polymerization reaction between a trimesoyl chloride (TMC) and each of the following three amines: 3,3-diamino-N-methyl-dipropylamine (DMDPA), nitrilotriethylamine (NTEA), and diethylenetriamine (DETA), on the surface of an asymmetric cellulose acetate (CA) membrane. The effects of the amine chemical structure and the interfacial polymerization conditions on the dehydration of an aqueous ethanol solution by pervaporation were investigated. To characterize the swelling behavior and the resulting free volume variation in the interfacially polymerized PA layers, the PA membranes in dry and wet (with aqueous ethanol solution) conditions were probed by positron annihilation lifetime spectroscopy (PALS). The difference between the o-Ps lifetime in the wet and that in the dry condition (Delta tau(3)=tau(3w)-tau(3d)) of the interfacially polymerized PA membranes increased in the following order: DETA-TMC < DMDPA-TMC < NTEA-TMC. The swelling effect induced by the aqueous ethanol solution was restricted by the crosslinking structure in the PA layer. This result corresponded well with that of the XPS analysis. The DETA-TMC/CA composite membrane prepared using the desirable interfacial polymerization conditions (immersion in the aqueous solution of 0.5 wff DETA for 10 s, and contact with the organic solution of 0.5 wff TMC for 5 s) exhibited the following desirable pervaporation performance in dehydrating an aqueous solution of 90 wt% ethanol at 25 degrees C: a permeation flux of 1220 g/m(2) h and a water concentration in permeate of 98.4 wt%. It was also found that the DETA-TMC/CA composite membrane exhibited superior performance compared to the composite membranes discussed in the literature. (C) 2012 Elsevier B.V. All rights reserved.