The polymerization of phenylacetylene in the presence of ferric acetylacetonate and triethylaluminum

The polymerization of phenylacetylene initiated by ferric acetylacetonate and triethylaluminum was studied over the temperature range −30°−70°, in bulk as well as in the presence of diluents, and over a range of catalyst compositions and concentrations. The product consisted of four major fractions: crystalline polymer of molecular weight about 7000 and a very narrow molecular‐weight distribution (MWD), (fraction I); somewhat lower‐molecular‐weight amorphous polymer with a broader MWD (fraction II); linear oligomer (fraction III); and the asymmetric cyclic triphenyl‐benzene (fraction IV). The average degree of polymerization, of fraction I (65–70) is independent of all polymerization variables, that is, temperature from −30° to 70°C, the presence or absence of diluent (tetralin or benzene), and catalyst concentration and composition. The MWD is narrow with M̄w/M̄n equal to 1.05 or less. The results suggest that thermodynamic rather than kinetic factors limit the size of the polymer. A possible mechanism is proposed.