Volume changes of poly(2-methylaniline)upon redox switching: anion and relaxation effects

E. M. ANDRADE; F. V. MOLINA; M. I. FIORIT; D. POSADAS

ELECTROCHEMICAL AND SOLID STATE LETTERS

The Electrochemical Society

Lugar: Princeton; Año: 2000 vol. 3 p. 504 - 507

1099-0062

The volume changes of poly(2-methylaniline) upon redox cycling in different acidic media was studied using voltammetric experiments with simultaneous microscopical observation. These experiments were performed with continuous potential cycling, and also after waiting at the negative potential limit until the polymer film is completely reduced and relaxed. The changes in the area occupied by the polymer film in the microscope images is taken as a measure of volume variations.During continuous potential cycling the film shows smooth, relatively low changes, showing hysteresis and dependence on the electrolyte anion. When the polymer is completely reduced and relaxed its volume reaches a minimum. The dimensional changes have a steep increase in the subsequent anodic scan, the overall change being about an order of magnitude higher than in continuous cycling, with little dependence on the electrolyte anion. During the cathodic scan the volume changes are similar to the stationary cycling experiments.     These results suggest that the volume changes are due to two different processes, the faster one being proton and anion exchange with the electrolyte, both carrying solvent molecules. The other process is a structural change of the polymer backbone, giving higher volume changes but having, during the reduction step, a much lower rate.