Poly(phenylacetylene) was selected for the central core molecule and synthesized polydendrons by the polymerization of monodendrons with the phenyleneethynylene repeating unit. In the differential scanning calorimetry (DSC) of the polydendrons, no glass transition temperature were detected. The well defined dendritic and rodlike structure of the polydendrons may also be effective for electrical conductive, nonlinear optical, and magnetic properties for substituted polyacetylenes.