Abstract
<p class="PaperAbstract"><span lang="EN-US">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.</span></p>
Highlights
In recent years there has been considerable interest in the development of stable conjugated polymers because of their potential use in a variety of applications that require materials which doi:10.5599/jese.225J
As we have discussed in Ref. [22], the bending beam method offers the possibility to measure the changes of the stress in thin polymer films but the contributions from surface and bulk cannot be separated in the general case, only the “voltdeflectograms”, i.e. the ΔR-1 vs. E plots are shown in Fig. 2. doi:10.5599/jese
The above experimental results support the mechanistic picture, according to which the originally compact and strongly adherent polymer films undergo structural changes during electrochemical degradation, and agree with earlier observations that the porosity of the film increases progressively during the degradation process. It can be seen from the scanning electron microscopy (SEM) images of overoxidized Au|PEDOT that the degradation process induces only a partial delamination of the polymer film from the underlying metal
Summary
In recent years there has been considerable interest in the development of stable conjugated polymers because of their potential use in a variety of applications that require materials which doi:10.5599/jese.225J. OVEROXIDATION OF POLY(3,4-ETHYLENEDIOXYTHIOPHENE) FILMS are both electrically conducting and mechanically compliant. Electronic and electrochemical devices based on organic materials are e.g. light emitting diodes, sensors, actuators, organic thin film transistors, solar cells, memory devices, ion-selective electrodes, microelectrode arrays, fuel cells, etc. [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] In all these applications the long term stability of the polymer is of particular concern. This stability can be assessed in terms of the property of interest, such as: mechanical elasticity, conductivity, electrochemical activity, etc
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