Spectroelectrochemistry of poly(o-phenylenediamine): Polyaniline-like segments in the polymer structure

A comparative discussion of the electrochemical and spectroelectrochemical properties of poly(o-phenylenediamine) POPD, an aromatic diamine, is presented. In situ conductance measurements show that POPD shows some conductance around the redox peak potentials, i.e. = −0.02 < ESCE < 0.00 V. In situ UV–vis and Raman spectroelectrochemical results suggest that radical cations of polyaniline (PANI)-like segments in POPD backbone might be responsible for imparting conductance to this otherwise nonconducting polymer (as commonly supposed in the literature). The presence of radical cations was confirmed by in situ Raman spectra showing a band at 1390 cm−1 characteristic of a C–N+-stretching vibration having an intermediate single/double bond character and being coupled to quinoid rings/polaronic form of PANI segments in the polymer. Results also reveal that POPD shows a close correlation between its electrochemical and spectroelectrochemical properties in the range of −0.02 < ESCE < 0.00 V, and provide support for the suggested presence of doped PANI-like segments in said potential range.