Interpretation of polyazulene electropolymerization considering faradaic current efficiency and capacitive current effects during the growth and redox

A theoretical analysis of the electropolymerization of azulene at a rotating ring-disk electrode is presented. This analysis provides a method for determining the current efficiency of electropolymerization. The oxidation of azulene to polyazulene in acetonitrile as solvent is a convective-diffusion controlled process that proceeds with 100% current efficiency. A positively charged site is associated with at least two non-terminal monomer units in the oxidized form of the polymer. Hydrogen ion has been identified and quantitated as a product of the electropolymerization process. No hydrogen ions are produced by the redox process involving only the polymer film. A theoretical analysis of rotating disk electrode, RDE, and rotating ring-disk electrode, RRDE, experiments established the advantages and limitations of these purely electrochemical approaches to the study of the growth phase of electropolymerization processes. The results are consistent with the simultaneous production of hydrogen ion and a reduced polymer, and charging the polymer by electrooxidation without producing hydrogen ions. The shift of the halfwave potential during the oxidation of azulene at a polymer coated electrode in the early stages of film growth demonstrates that the mechanism of electropolymerization continues to change until relatively thick polymer films have formed.