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 (F TIR) spectroscopy using the attenuated total reflection method and by the e lectrochemical quartz crystal microbalance, EQCM, technique. The polymer ma terial has been synthesized by electrochemical reduction of alpha,alpha,alp ha',alpha'-tetrabromo-p-xylene on a Pt-electrode in dimethylformamide or ac etonitrile using tetraethylammoniumtetrafluoroborate or tetraethylammoniumt osylate as electrolyte salts. The IR spectra of the doped conducting state show a very large broad absorption band starting at 1700 cm(-1) and extendi ng to 5000 cm(-1). Additional changes in the spectra can be seen in the reg ion between 1700 and 700 cm(-1) where new absorption bands appear. The inte nsity for these infrared active vibrations (IRAV) increase with increasing n-doping level. The reversible charging-discharging reaction is characteriz ed by the growth in intensity of the IRAV during charging and diminish duri ng discharging of the PPV film. Results from FTIR spectroscopy obtained fro m the charging-discharging reaction are consistent with the results obtaine d from the EQCM experiments, which show movement of counter cations during n-doping. (C) 2001 Elsevier Science B.V. All rights reserved.