Electrochemical synthesis and redox processes of poly(paraphenylene vinylene): An in situ FTIR-attenuated total reflectance and electrochemical quartz crystal microbalance study

The electrochemical synthesis and the redox reactions of poly(paraphenylene vinylene) (PPV) have been studied by in situ Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflection method and by the electrochemical quartz crystal microbalance, EQCM, technique. The polymer material has been synthesized by electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene on a Pt-electrode in dimethylformamide or acetonitrile using tetraethylammoniumtetrafluoroborate or tetraethylammoniumtosylate as electrolyte salts. The IR spectra of the doped conducting state show a very large broad absorption band starting at 1700 cm⁻¹ and extending to 5000 cm⁻¹. Additional changes in the spectra can be seen in the region between 1700 and 700 cm⁻¹ where new absorption bands appear. The intensity for these infrared active vibrations (IRAV) increase with increasing n-doping level. The reversible charging–discharging reaction is characterized by the growth in intensity of the IRAV during charging and diminish during discharging of the PPV film. Results from FTIR spectroscopy obtained from the charging–discharging reaction are consistent with the results obtained from the EQCM experiments, which show movement of counter cations during n-doping.