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 thickness, counter-anions and film conditioning on the response are studied. It is demonstrated that the response can vary from anionic to cationic, depending on the charge-compensating counter-anion (doping anion) incorporated during electropolymerization. Furthermore, the ionic response may be altered by redox couples in the solution, and under some conditions polypyrrole may also act as a pure redox electrode. The mixed ionic and redox sensitivities of polypyrrole are explained by considering both ion and electron transfer at the polymersolution interface. The experimental results are related to a theoretical model developed for p-type conducting polymers