A THERMODYNAMIC APPROACH TO THE INTERPRETATION OF ANODIC AND CATHODIC DOPING OF POLY(3-METHYLTHIOPHENE)

: VISY C, LUKKARI J, KANKARE J

Publisher: ELSEVIER SCIENCE SA LAUSANNE

: 1991

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry

: JOURNAL OF ELECTROANALYTICAL CHEMISTRY

: J ELECTROANAL CHEM

: 319

: 1-2

: 85

: 100

: 16

: 0022-0728

DOI: https://doi.org/10.1016/0022-0728(91)87069-G

Anodically and cathodically conducting poly(3-methylthiophene) have been studied by transient and steady-state spectroelectrochemical methods in the presence of different anions (ClO4-, PF6-) and cations (Bu4N+, Dec4N+) in acetonitrile solution of low water content. Spectral differences obtained with different ions are interpreted by assuming segments of different effective conjugation lengths in the neutral polymer determined by an interaction between the anions and the chains during the electrochemical preparation of the film. A redox mechanism based on thermodynamic considerations is suggested to describe the anodic and cathodic doping of thiophene-type conducting polymers. Both dopings start with the electrochemical transformation of species of longer effective conjugation length. Cyclic measurements are strongly controlled by non-equilibrium or quasi-reversible effects explained by the assumption of a two-phase system resulting in the undoping not being the simple inverse process of doping.