Spectroscopic and electrochemical studies of charge transfer in modified electrodes

Abstract

Experimental results from electrochemical e.s.r. on electrodes modified with conducting polymers such as polyaniline, polypyrrole and polythiophene are presented. The results show that the polymer exists in two forms, one stable when it is insulating (α) and the other (β) when it is conducting. In the conducting region the kinetics of the transformation of the metastable α form into the β form can be followed by e.s.r. It is further shown that in the lightly oxidised films there is a one-to-one correlation between charge injected and e.s.r. spins. These results are explained by a chemical redox model as opposed to a delocalised band.Results from a.c. impedance studies are presented. These results are explained by an equivalent circuit which includes a novel transmission line with differential resistances. Theoretical impedance plots are derived. Experimental results show that the polymer resistance and the resistance of the aqueous pores are equal. Reasons for this finding are discussed.