Doping of polyaniline by transition-metal salts

Complexes of some transition-metal salts and emeraldine base of polyaniline were synthesized and characterized by UV-vis-IR spectroscopy, morphology studies, and conductivity measurements. Depending on the inorganic salt used, two extreme cases of doping were distinguished. The first regime of doping resulted in films of grained morphology, with a relatively high conductivity of up to 10(-1) S/cm and electronic absorption spectra showing features of both pseudo-protonic doping and oxidation of the polymer backbone. IR absorption spectra were consistent with interaction of the benzenoid groups of the polymer with metal cations. The second regime of doping resulted in a smoother film morphology without grains, but with poor conductivity, normally not more than 10(-3) S/cm, and higher solvent concentration in the film. Electronic and IR absorption spectra were consistent with pseudo-protonation of the polymer backbone. On the basis of the obtained data, a model of the macromolecular polyaniline-transition-metal salt complex is proposed.