Structural changes during the overoxidation of electrochemically deposited poly(3,4-ethylenedioxythiophene) films

  • Maria Ujvari Institute of Chemistry, Laboratory of Electrochemistry and Electroanalytical Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
  • Gyözö G. Láng Institute of Chemistry, Laboratory of Electrochemistry and Electroanalytical Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
  • Soma Vesztergom Institute of Chemistry, Laboratory of Electrochemistry and Electroanalytical Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
  • Krisztina J Szekeres Institute of Chemistry, Laboratory of Electrochemistry and Electroanalytical Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
  • Noémi Kovács Institute of Chemistry, Laboratory of Electrochemistry and Electroanalytical Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
  • Jeno Gubicza Institute of Physics, Department of Materials Physics, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest
Keywords: Conducting polymers, PEDOT, Degradation, Delamination, Crystalline phase

Abstract

Electrochemical, mechanical and morphological properties of thin poly(3,4-ethylenedioxy-thiophene) (PEDOT) films deposited on gold were investigated in aqueous sulfuric acid and sodium sulphate solutions. At sufficiently positive electrode potentials overoxidation of the polymer took place and resulted in morphological changes and structure evolution. These effects were monitored by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction. Significant changes in the film stress caused by overoxidation were detected by using the electrochemical bending beam method. Results of the EIS measurements proved that the charge transfer process at the metal/film interface is more hindered in case of the degraded film. According to SEM images the overoxidation/degradation of PEDOT films can result in random-like but quite well-ordered arrays of islands and trench-like structures. The diffraction peaks of PEDOT became sharper and more intensive during the subsequent oxidation cycles indicating an increase in the degree of crystallinity of the polymer.

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Published
21-04-2016