Voltammetric study of the reduction and relaxation of poly(o-toluidine). Effect of the polymer thickness and the external electrolyte nature and concentration

MARÍA JOSÉ RODRÍGUEZ PRESA; DIONISIO POSADAS; MARÍA INÉS FLORIT

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

ELSEVIER

Lugar: Amsterdam; Año: 2000 vol. 482 p. 117 - 124

0022-0728

The reduction and relaxation of poly(o-toluidine) (POT) was studied as a function of the wait time at different waiting potentials near the reduction potential of the polymer. The influence of the film thickness, the acid concentration, and the ionic strength of the external electrolytic solution on these processes were also studied. Two types of electrolytes were employed: perchloric and sulfuric acid. Both the reduction and the relaxation times depend on the proton concentration of the external electrolyte media and on the film thickness. They are independent of the ionic strength and, in a limited range, of the waiting potential. The voltammetric response of fully reduced and relaxed polymers shows that, at low sweep rates, the kinetics are controlled by slow ionic movements within the polymer. Experiments with medium exchange show that, once the polymer is fully reduced and relaxed, its state is independent of the composition and concentration of the electrolyte in which this particular state was obtained. Furthermore, they also show that the shape of the voltammetric oxidation profile depends exclusively on the composition and concentration of the electrolyte in which the polymer is being oxidized. This means that the effect of the solution composition and concentration is manifested only through the participation of protons and anions in the mechanism of oxidation of the polymer.