A fast controlled synthesis of poly(p-phenyleneethynylene)s under transition-metal-free conditions

A transition-metal-free polymerization of an AB-type monomer for the synthesis of well-defined poly(p-phenyleneethynylene)s is described. The polymerization of 1-pentafluorophenylethynyl-4-[(trimethylsilyl)ethynyl]benzene with a catalytic amount of tetrabutylammonium fluoride or potassium t-butoxide in the presence of cryptand[2.2.2] affords polymers within a few minutes. When monitoring the polymerization, the molecular weight as a function of monomer conversion shows a linear relationship, where the polydispersity indexes are around 1.6. The polymerization proceeds predominantly via intramolecular fluoride anion transfer to the polymer end. End capping of the active polymerization end is also demonstrated.