Dimethyltitanacene, in conjunction with a wide variety of compound containing Si-H bonds, is an excellent catalyst for the polymerization of acetylene to give free standing films. Polymerizations of acetylene in a variety of siloxane and silane matrices; using this’ catalyst system are described. The polyacetylenes produced with a [-(Me-SiHO-)(3)-(Me(2)Si)(17)-](n) random copolymer showed very similar properties to those previously produced by Naarman et al. with a Shirakawa-type catalyst in a polydimethyl-siloxane matrix. Ring, or chain, poly(methylhydrosiloxanes) with higher proportions of -(MeSiHO)- undergo redistribution in the course of acetylene polymerization to give polyacetylene embedded in an insoluble polysiloxane glass. Polyacetylene produced in a poly(phenylsilane) matrix yielded a 2-component material from which the polysilane could not be solvent extracted. The electrical conductivity of iodine doped samples of this material is somewhat lower than that of the pure polyacetylene, but its mechanical properties and its resistance to degradative oxidation are superior to those of either of the pure component polymers.