Polythiophene oxidation: Rate coefficients, activation energy and conformational energies

Polythiophene films reduced by prepolarization at different cathodic potentials were used as the initial states for their potentiostatic oxidation. At the chronoamperometric maxima the oxidation occurs under chemical kinetic control. The oxidation kinetic characteristics: rate coefficient (k), activation energy (Ea) and the reaction order of the oxidation reaction, change as a function of the cathodic potential of prepolarization. That means that k and Ea for the oxidation are functions of the oxidation overpotential, as for any oxidation kinetics, and of the cathodic potential of prepolarization. Rising cathodic potentials of prepolarization promote decreasing rate coefficients, k, and increasing Ea. Those variations are described by the electrochemical relaxation model. The activation energy includes two components: the constant activation energy of the electrochemical reaction and the conformational activation energy of the initial packed conformations that increases as the prepolarization potential rises.