Thin films of oligomers were synthesized on PTFE substrates and they were studied for separation of product from liquid chemical reaction mixture. Three different types of membranes were fabricated using a technique called ‘covalent molecular assembly’. Covalent molecular assembly is a synthesis technique in which a substrate is sequentially immersed in chemical solutions to grow molecular moieties with covalent bonding to the underlying layer of molecules on the substrate. The first membrane was oligoimide PMDA-ODA. The second membrane was crosslinked oligoamide TC-TAB. The third membrane was Nickel terminated oligoimide Ni-PMDA-ODA. The first two membranes were studied for Friedel-Crafts’ alkylation reaction between benzene and methyl chloride in presence of ferric chloride catalyst. With 30psia chloromethane pressure, the reaction proceeded to 100% conversion and the first two membranes provided a permeate of 99% pure toluene product. The third membrane was catalytically active to convert p-nitrophenol to p-aminophenol in presence of sodium borohydride in ethanol. The purity of the permeate stream reached 98% in 40 min and was stable for 2 h. Thus, novel membranes were synthesized for enhanced separations.