MECHANISM OF IONIC AND REDOX SENSITIVITY OF P-TYPE CONDUCTING POLYMERS .2. EXPERIMENTAL-STUDY OF POLYPYRROLE

The potentiometric response of polypyrrole films is studied. The films are electrochemically deposited on platinum. The effects of film thic kness, counter-anions and film conditioning on the response are studie d. It is demonstrated that the response can vary from anionic to catio nic, depending on the charge-compensating counter-anion (doping anion) incorporated during electropolymerization. Furthermore, the ionic res ponse may be altered by redox couples in the solution, and under some conditions polypyrrole may also act as a pure redox electrode. The mix ed ionic and redox sensitivities of polypyrrole are explained by consi dering both ion and electron transfer at the polymer\solution interfac e. The experimental results are related to a theoretical model develop ed for p-type conducting polymers