Electrochemical quartz crystal microbalance investigation of the ion exchange mechanism in the first oxidation step of polyaniline in HClO4

MARIA C. MIRAS; CESAR A BARBERO; RUEDIGER KOETZ; OTTO HAAS

JOURNAL OF ELECTROANALYTICAL CHEMISTRY - (Print)

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 1994 vol. 369 p. 193 - 197

1572-6657

The ion exchange of polyaniline thin films during the leucoemeraldine-emeraldine transition was investigated for different concentrations of HClO4 using an electrochemical quartz crystal microbalance (EQCM). At pH 2 the mass increase on oxidation indicates that anions are inserted in order to compensate for the positive charge in the oxidized polymer. At higher acid concentrations (> 2 M), a clear mass decrease is observed at the beginning of the first oxidation step. This constitutes direct evidence that protons are expelled at the beginning of the first oxidation step. For 4 M HClO4 the molar mass equivalent of the species exchanged is close to − 20 g mol−1, which would correspond to the mass of an expelled hydronium ion. The two distinct slopes observed in the frequency-charge plots can be used for an improved quantitative analysis of the relative contributions of ClO4− and protons to the overall ion exchange process in the first oxidation step of polyaniline.