In Situ Conductivity, Electron Spin Resonance and Absorption Spectra Measurements in Polyaniline During Electrochemical Doping

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Abstract
In in situ measurements of ESR during electrochemical doping in polyaniline, the maximum spin density is observed at 3.25 V. ESR linewidth decreases upon doping, but after exhibiting a minimum value at 3.5 V, it increases again, tending to saturation. On the other hand, in situ conductivity measurement demonstrates the maximum value (1.6 S/cm) at around 3.5 V. Taking into consideration the complex absorption spectral change upon doping, the results are discussed in terms of polaron and bipolaron models. At higher doping levels, suppression of the interchain transfer of polaronic species due to Coulomb interaction is introduced to explain the decrease of conductivity.