MECHANISM OF IONIC AND REDOX SENSITIVITY OF P-TYPE CONDUCTING POLYMERS .1. THEORY

Equations have been derived to describe the open-circuit potentiometri c response of a p-type conducting polymer membrane, The final model is derived step by step from the model of a single-metal electrode by us ing the concept of solvated electron and from the model of a solid-sta te ion-selective and/or electron-selective electrode containing a spar ingly soluble metal-rich salt in the membrane. All electrodes consider ed, i.e. the metal, ion-selective and polymer electrodes, are presente d as systems based on an ionic salt of the M+e- type. The ionic and re dox sensitivities of a p-type conducting polymer are described by assu ming two possible equilibration pathways. In the first approach the io n-electron exchange process at the polymer surface without a change of the oxidation state of the polymer is discussed and in the second the metathesis of the polymer surface with a concurrent change in the oxi dation state of the polymer is considered. The equations derived allow us to interpret the anionic, cationic and redox sensitivities and to discuss the observed changes in the standard potentials.