AbstractIn order to improve the separation characteristics of membranes for pervaporation, the introduction of fluoroalkyl groups into poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) was achieved by two methods. First, 3,3,3‐trifluoropropyldimethylsilylated PTMSP was prepared via metalation of PTMSP followed by treating with 3,3,3‐trifluoropropyldimethylchlorosilane. About 6 mol % of 3,3,3‐trifluoropropyldimethylsilyl group was introduced by the polymer reaction. Second, the copolymerizations of 1‐trimethylsilyl‐1‐propyne (TMSP) with 1‐ (3,3,3‐trifluoropropyldimethylsilyl)‐1‐propyne (FPDSP) or 1‐ (1H,1H,2H,2H‐tridecafluorooctyldimethylsilyl)‐1‐propyne (FODSP) were carried out to afford TMSP/FPDSP or TMSP/FODSP random copolymers. The ratio of TMSP monomer unit and the comonomer unit, x/y, was in the range of 99/1‐85/15. All the chemically modified PTMSP membranes showed ethanol permselectivity for pervaporation of aqueous ethanol solution. In particular, the introduction of less than about 5 mol % of fluoroalkylsilylated units into PTMSP effectively enhanced the selectivity. However, excess introduction of FODSP comonomer unit caused a decrease of the selectivity, with the value being smaller than that of PTMSP membrane. Furthermore, tetrahydrofuran, acetone, acetonitrile, dioxane, and isopropanol were efficiently separated from their dilute aqueous solutions using a TMSP/FPDSP copolymer membrane.