Cation exchange behavior during the redox switching of poly (3,4-ethylenedioxythiophene) films
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ORIGINAL PAPER
Cation exchange behavior during the redox switching of poly (3,4-ethylenedioxythiophene) films Violeta-Tincuţa Gruia 1 & Adriana Ispas 1
&
Igor Efimov 2 & Andreas Bund 1
Received: 30 April 2020 / Revised: 17 August 2020 / Accepted: 18 August 2020 # The Author(s) 2020
Abstract Poly (3,4-ethylenedioxythiophene), PEDOT, films were synthesized at room temperature by potentiodynamic and potentiostatic step deposition in aqueous solutions containing EDOT monomer and LiClO4. In some solutions, the effect of small amounts of sodium dodecylsulfate, SDS, on the polymerization rate of EDOT and on the stiffness of the obtained PEDOT film was studied. The obtained PEDOT films were transferred in aqueous solutions containing cations with different molar mass, such as H+, Li+, Na+, K+, and Cs+. The apparent molar masses of the exchanged species during potentiodynamic experiments were determined by in situ microgravimetry. These measurements underlined the importance of the electrolyte chosen for electropolymerization process. It is known that SDS anions can be trapped inside the polymer layer during electropolymerization, providing them with a cation exchange behavior. However, even if the PEDOT films were deposited from an electrolyte without SDS, they still acted as cation exchangers. Keywords PEDOT . Cation exchange . EQCM . Electropolymerization . SDS
Introduction Poly (3,4-ethylenedioxythiophene), PEDOT, is one of the conductive polymers that is intensively studied due to its excellent properties, such as good electrochemical and thermal stability, biocompatibility, flexibility, and high conductivity, just to name a few [1–3]. It is well known that organic charge transport materials, a class to which the conductive polymers belong, can be divided into p-type and n-type materials. Usually, the conductive polymers can be doped via chemical and the electrochemical approaches [4], so that both states, p-doped (oxidized) and ndoped (reduced), can be realized. The process involved in pElectronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04809-6) contains supplementary material, which is available to authorized users. * Adriana Ispas [email protected] 1
Electrochemistry and Electroplating Group, Technische Universität Ilmenau, Gustav-Kirchhoff-Str. 6, 98693 Ilmenau, Germany
2
Department of Chemistry, Materials Center, University of Leicester, Leicester LE1 7RH, UK
doping is equivalent to withdrawing electrons from the π-system of the polymer backbone. This results in a positively charged unit in the conductive polymer [4, 5]. Electrons are introduced into the π-system of the polymer backbone for ndoping, and a negatively charged unit in the conjugated system is thus formed [4, 5]. p-doped PEDOT films can be used as positive electrodes in batteries [6–9], in microlithography [10], for corrosion inhibition [11], in solar cells [12] or in sensors [13–21]. It was observed that some conformational changes occur in a conductive polymer film when it is
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