The Effect of Temperature on the Impedance of Poly-O- Toluidine in 3.7 M H2SO4

MI FLORIT,; D POSADAS,; F. V. MOLINA; E. M. ANDRADE

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

The Electrochemical Society

Lugar: Princeton; Año: 1999 vol. 146 p. 2592 - 2597

0013-4651

The impedance response of poly(o-toluidine) (POT) electrochemically grown films was investigated in sulfuric acid 3.7 M, in the temperature range 218 to 293 K. The Nyquist diagrams as a function of temperature show that the transition potential from the nonconduclive to the conductive state shifts in the positive potential direction as the temperature decreases. This implies that, at low temperatures, a greater field is needed to induce the transition. In the nonconductive slate both the high-frequency and the low­ frequency resistances increase as the temperalure is decreased. The Arrhenius plots for both show a break at about 255 K. This is in agreement with the fact that the high-frequency resistance is control!ed by ionic movements and that there is charge-transfer con­trol at the polymer/solution interface. In the conductive state the low-frequency capacitance is independent of temperature, show­ing that the active site concentration does not depend on the temperature. The low-frequency resistance in this potential region also depends on the temperature. No break is observed in the Arrhenius plot for this quantity. However from its slope it is inferred that ionic motions within the polymer control the charge transport in this state.