Polyaniline films electrodeposited on iron from oxalic acid solution: spectroscopic analysis of chemical structure

Chemical structure of polyaniline electrodeposited on iron from oxalic acid solution has been studied by means of NEXAFS, Raman, and XPS spectroscopies. The effect of the duration and synthesis conditions (polarization mode, potentials, stirring of the solution) has been analyzed. The as-formed PANI films have revealed a relatively low degree of protonation. It has been shown that stirring of electrolyte has the greatest effect on the chemical structure of the polymer. The deposition from the stirred solution provides smooth and chemically homogeneous films, whereas the deposition from quiescent solutions favors the precipitation of polyaniline particles enriched in pernigraniline fragments. The obtained XPS results verify the adsorption of the polymer through the N2p-Fe3d donor-acceptor interaction between iron atoms and amine groups of polyaniline chains in the film nuclei. The nitrogen K edge NEXAFS spectra, which are very sensitive to the protonation of chains and electronic delocalization, vary significantly, depending on the conditions of PANI electrodeposition.