Self-doping of polyaniline prepared with the FeCl3/H2O2system and the origin of the Raman band of emeraldine salt at around 1375 cm−1

• DOI: 10.1002/pi.4983
• Publication Date: 2015-08-20T06:47:06Z
• Authors: Michal Bláha; Jiří Zedník; Jiří Vohlídal
• Keywords: 01 natural sciences; 0104 chemical sciences

Stepwise addition of H2O2 in small portions into the polymerization mixture reduces the number of defects in polyaniline (PANI) prepared with the Fe3+/H2O2 system, although it does not eliminate them completely. PANIs slightly self-doped with phenolic groups are thus obtained, which show conductivity from 2.65 to 0.38 S cm−1 as the total H2O2/aniline mole ratio is increased from 0.125 to 1.25. The conductivity shows a good correlation with the AB/A900 UV−visible absorbance ratio of the PANI emeraldine salt form (PANI ES), much better than with the AB/AQ ratio of the corresponding emeraldine base form. This corresponds well with the assignment of the band at 900 nm to polaronic transitions. Partial self-doping of PANIs with weakly acidic phenolic groups allowed evidence to be obtained for the assignment of Raman bands at 1370 cm−1 and 734 cm−1 (for λexc = 780 nm) to vibrational modes of highly localized polarons. The presence of the band at 880 cm−1 in the IR spectra of these PANI ES samples that are totally free of sulfate ions proves that this band is associated with a vibrational mode of PANI ES and need not be assigned to a mode of HSO4− ions, as has been suggested by some authors. © 2015 Society of Chemical Industry