Conducting Polymer Iongels Based on PEDOT and Guar Gum

Conducting polymer hydrogels are attracting much interest in biomedical and energy-storage devices due to their unique electrochemical properties including their ability to conduct both electrons and ions. They suffer, however, from poor stability due to water evaporation, which causes the loss of mechanical and ion conduction properties. Here we show for the first time a conducting polymer gel where the continuous phase is a nonvolatile ionic liquid. The novel conducting iongel is formed by a natural polysaccharide (guar gum), a conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT), and an ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BMIMCl). First, an aqueous dispersion of PEDOT:guar gum is synthesized by an oxidative polymerization process of EDOT in the presence of the polysaccharide as stabilizer. The resulting PEDOT:guar gum was isolated as a powder by removing the water via freeze-drying process. In the final step, conducting iongels were prepared by the PEDOT:guar gum mixed with the ionic liquid by a heating-cooling process. The rheological properties show that the material exhibits gel type behavior between 20 and 80 °C. Interestingly, the conducting polymer iongel presents redox properties as well as high ionic conductivities (10^-2 S cm^-1). This material presents a unique combination of properties by mixing the electronic conductivity of PEDOT, the ionic conductivity and negligible vapor pressure of the ionic liquid and the support and flexibility given by guar gum.