The kinetic behavior for the electrochemical polymerization of aniline in aqueous solution

The electrochemical oxidation of aniline in 0.8 M HCl solution is carried out using repeated potential cycling between 0 and 1.1 V (versus SCE). Its anodic peak current at 1.0 V for the first scan is markedly retarded in the presence of resorcinol or phloroglucinol, and decreases with increasing their concentrations. However, this peak current is slightly affected by hydroquinone, because it is oxidized electrochemically before oxidation of aniline. The experiment of the rotating ring-disk electrode shows that both the disk current at 1.0 V and the ring current for electrolysis of aniline are simultaneously decreased in the presence of resorcinol. This means that a soluble intermediate cation generated at the disk electrode is captured by resorcinol. There are four anodic peaks and three reduction peaks on the cyclic voltammograms during oxidation of aniline by repeated potential cycling. From the temperature dependence of the separate anodic peak currents, the activation energy of each reaction is calculated. For the first scan, the oxidation of aniline at 1.0 V involves two different activation energies at temperatures from 1 to 35 degrees C. Both activation energies are smaller than 21 kJ mol(-1). The values fall into the range of activation energies for a general propagation reaction and termination reaction of free radical polymerization. These experimental facts indicate that the initial stage of aniline oxidation is the most likely to involve the formation of a radical cation.