Facile Li/HMPA-Promoted Polymerization Method for the Synthesis of SolublePoly(phenylenes)

摘要

A synthesis of poly(phenylene) is described by the treatment of 1-bromo-4-lithiobenzene with hexamethylphosphoramide (HMPA). The polymerization occurred nearly instantaneously even at -78 C. Conditions have been optimized using dioxane as a solvent and HMPA addition at 70-80 C to afford poly(phenylenes) that are predominantly para-linked. The polymers are soluble in THF, dichloromethane, and chloroform. Analysis of the initially formed polymers showed that there was a high bromide content (approximately one bromide for every three aryl rings). Debromination of the material was achieved by treatment with butyllithium and quenching with water. The MW of the debrominated polymer was 3178 by SEC analysis. Functionalization of the polymer was demonstrated by the lithium-halogen exchange on the initially formed brominated polymer followed by quenching with carbon dioxide to afford the carboxylated polymer. The brominated and debrominated polymers were shown to be electroactive.