INSITU ESR OF POLYANILINE BY ELECTROCHEMICAL DOPING - POLARON TO PAULI-LIKE INSTEAD OF POLARON TO BIPOLARON

Polyaniline film was synthesized electrochemically with HBF4 as an electrolyte. A potential was changed step by step to measure ESR spectra. At low doping levels ESR line shape was found to be a single Lorentzian. At higher doping levels, however, it was composed of double Lorentzians; narrow line and broad one. An integral intensity of the broad line becomes larger than that of the sharp one at the higher potentials. Temperature dependence of spin susceptibility suggested that the sharp line behaves as a Curie spin and the broad one does as a Pauli one, which is consistent with low frequency ESR result on the chemically prepared emeraldine salt with BF4-. The sharp line can be interpreted as a polaron created in an initial stage of the electrochemical doping. Presumable origin of the broad line was discussed.