Synthesis, properties, and membrane-separation functions of a novel fluorine-containing poly(phenylacetylene) were examined. The monomer used was [o-n-(perfluorohexyl)phenyl]acetylene, which has a rigid rod-like ortho-substituent. Polymers, whose intrinsic viscosities ([eta]) were ca. 0.4-2.2 dL/g, were obtained in high yields with various W and Mo catalysts. The MoCl5-Ph(3)Sb catalyst achieved the highest [eta] of 2.25 dL/g corresponding to an M(w) over one million. The polymer was a brown solid soluble only in F-containing solvents such as n-(CF3)(2)C6H4. The oxygen permeability coefficient of the polymer membrane was 90 barrers, which is the second highest among those of ortho-substituted poly(phenylacetylenes). In the pervaporation of an ethanol-water mixture, the polymer membrane showed ethanol permselectivity [alpha(EtOH/H2O) = 1.7].