Photographic measurements of propagation speeds of the conducting zone in polyaniline films during electrochemical switching

A physical interpretation of impedance at conducting polymer/electrolyte junctions

“…These elements include a resistor to describe transport in the electrolyte, a capacitor (usually modeled with a constant phase element) in parallel with a charge transfer resistor to model the process of ion injection into the film, and a diffusion element (modeled with a Warburg or a constant phase element) to capture ion diffusion inside the polymer. 20 An alternative approach to study ion injection and transport in conjugated polymers is the socalled "moving front" experiment, [21][22][23] which relies on the fact that the optical absorption spectra of these materials change upon doping (electrochromism). In this experiment, changes in the optical density are spatially and temporally resolved in order to infer the injection and transport of ions inside a polymer film.…”

An interpretation of small values of the transfer coefficient at conducting polymers

“…A physical meaning of this variation is that the term, vðÀxÞ shows a larger variation with the current than vðxÞ because of the stronger electric field effect in the more resistive domain. This deviation has been found in the plots for polyaniline [4,5] and polypyrrole films [6,8], as shown in Fig. 4.…”

“…In order to evaluate the transfer coefficient from the growth experiment of the conducting zone, we have measured distances of the conducting front from the electrode at various electrolysis times after a given electrode potential is applied to the electrode [4][5][6]16]. The current density should be proportional to the velocity of the moving front if the growing domain is rectangular.…”

“…When a conducting polymer in the insulating state is switched electrochemically into the conducting state in sufficient concentrations of dopant ion, the conducting zone grows clearly from the electrode at the expense of the insulating domain [4][5][6][7][8][9][10][11]. The growth occurs in the direction normal to the electrode.…”

“…The rate is predicted to be expressed by the Tafel or the Butler-Volmer equation. When the Tafel type equation was applied to the relation between the propagation rate and the electrode potential, the transfer coefficient evaluated from the plot of the logarithms of propagation rate against the applied potential was close to 0.1 for polypyrrole [8,21] as well as for polyaniline [4,5]. This value is extraordinarily small in comparison with conventional values close to 0.5 [22].…”