27 July 2004 Revisiting the electrochemical properties of conducting polymers
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Free-standing polypyrrole (ppy) films 10-20mm thick were obtained by electropolymerization on metals and subsequent peeling off. The free-standing film can be reduced in aqueous solution up to -3.0 V without any presence of hydrogen release or polymer degradation, keeping a conductivity high enough to allow their use as electrode for elecromehanical reactions. Voltammetric experiments inside the polymer oxidation/reduction potential range show that the involved charge increases for decreasing sweep rates. A deep reduction of the film requires polarization times longer than 300 s at -0.6V or more cathodic potentials. According with the voltammetric (dynamic) reduction. Around -1.0V the polymeric structure is closed when still a 35 to 60% (depending on the scan rate) of the material remains oxidized. The reduction then goes on by slow migration of the counterions through the increasingly compacted polymetric entanglement by stimulating confrontational relaxation movements of the ppy chains. The cathodic maximum, appearing on the voltammograms between -.7 and -0.9V, is related to slow kinetic and structural processes since the film reduction is completely by long polarization time at -0.6V. Three potential windows are distinguished for these films in a aqueous solutions: from potentials a low as -3.0 to -0.6V the free-standing film is a compacted semiconducting electrode; from -0.6 to +0.5 V is a stationary oxidation/reduction region; at stationary higher potentials than +0.6V a degradation of the electromechanical activity occurs.
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Toribio F. Otero, Toribio F. Otero, Maria Jesus Ariza, Maria Jesus Ariza, S. O. Costa, S. O. Costa, Manuel Marquez, Manuel Marquez, } "Revisiting the electrochemical properties of conducting polymers", Proc. SPIE 5385, Smart Structures and Materials 2004: Electroactive Polymer Actuators and Devices (EAPAD), (27 July 2004); doi: 10.1117/12.538604; https://doi.org/10.1117/12.538604

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