Surface modification of cellulose acetate (CTA) membranes was achieved by subjecting them to magnetron-enhanced plasma. Plasma polymerization and deposition of thiophene were achieved on these membranes in a nitrogen atmosphere. Such modified membranes were characterized by determining the rate of deposition, angle of contact with water, and IR spectroscopy. The morphology of deposition was studied by SEM, and it was found that the globular particles grow with time to give a honeycomb or platelet structure. The water vapor transmission rates were measured and were found to decrease with an increase in the time of deposition. The pervaporation process of such modified CTA films for the separation of an isopropanol-water mixture was investigated. The water selectivity of the modified membranes was found to be increased.