Two-step cathodic synthesis of poly(para-phenylenevinylene)

The electrochemical behavior of a film, which consists of intermediate products of the α,α,α′,α′-tetrabromo-para-xylol (TBX) reduction and is deposited on a glassy-carbon electrode from 5 × 10^?2 M TBX solutions, is studied in 0.1 M Bu₄NBF₄ solution in DMFA by cycling the potential from 0 to ?1.4 V with respect to an aqueous saturated calomel electrode. When the potential is cycled from 0 to ?2.1 V in a cell filled with the supporting electrolyte, the film, which is assumed to have the (-BrHC-C₆H₄-CHBr-)_n composition, can be reduced to form poly(para-phenylenevilylene) (PPV). This film exhibits redox activity in the cathodic range in solutions of Bu₄NBF₄ in DMFA and in both cathodic and anodic ranges in solutions of Bu₄NBF₄ in AN. It is observed for the first time that, if the cathodic limit of the potential cycling range is extended to ?2.5 V, the cathodic doping of PPV at potentials below ?2 V disappears and a new reversible redox process takes place at more negative potentials.