The electrooxidation of phenylacetylene (PA) in acetonitrile (0.1 M in LiCiO(4)) produced poly(phenylacetylene). The product was isolated, purified, and characterized. Spectroscopic data showed the trans structure of the polymer. A radical reaction mechanism was proposed in which the oxidation of PA led to the formation of a PA radical in solution, which initiated a radical polymerization. The theoretical treatment for the radical mechanism yielded a reaction rate equation identical to the experimental one. The average molar mass was determined by gel permeation chromatography to be approximately 3100. © 2005 Wiley Periodicals, Inc.