In situ spectroelectrochemical and rotating ring-disk electrode studies on the initial states in the reductive electropolymerization of poly(p-phenylene vinylene)

The reductive coupling reactions in electrochemical polymerization of poly(p-phenylene vinylene) (PPV) have been studied by in situ UV-vis spectroscopy using lithographic galvanic microstructured metal foils (LIGA structure) as the working electrode, in situ UV-vis-ESR spectroscopy, and by the rotating ring-disk electrode (RRDE) technique. The polymer film was synthesized by electrochemical reduction of the monomer alpha,alpha,alpha',alpha'-tetrabromo-p-xylene (1) in dimethylformamide using tetraethyl ammonium tetrafluoroborate as the supporting electrolyte. The results show that the reduction of monomer 1 takes place in two steps. The first step is a two-electron reduction process leading to formation of intermediates that stay in solution without precipitation onto the electrode surface. The second two-electron reaction of these intermediates produce oligomers which precipitate onto the surface of the electrode. It was observed that the electrode material, cell design, and temperature have a marked influence on the value of the peak potential of the second reduction reaction.