Factors affecting the electropolymerization of aniline from aqueous solutions

Summary form only given. Electropolymerization of aniline and the synthesis of conducting polyaniline films on Pt-disc electrodes from a deoxygenated solution of 0.1 mol dm/sup -3/ aqueous background electrolytes containing aniline will be described. Results show that the rate of polymerization and the conductivity of polymer depend on various factors such as nature of the background electrolyte, pH of the medium, applied potential, etc. Cyclic voltammograms show that polyaniline is non conducting if grown from a medium of pH above 3, below ca. 0.6 V (wrt SCE). The peak positions and currents of cyclic voltammograms are greatly influenced by the anion of the background electrolyte. Also the cyclic voltammograms recorded at various scan rates are used to analyze the polymerization mechanism. Although the peak current is found to be proportional to the square root of the scanning rate, the other conditions for reversible electron transfer are not satisfied. Data fit closely with the ECE mechanism. Also polyaniline shows a spectrum of colours with the change of potential. For instance, it is dark blue at about +0.7 V which changes to Greenish blue at + 0.20 V, Green at +0.10 V, light green at - 0.40 V and yellow at - 0.60 V all with respect to SCE. N-methyl substitutions enhances the intensities of the colours.