High ionic conductivity and mechanical strength of solid polymer electrolytes based on NBR/ionic liquid and its application to an electrochemical actuator

In this study, a dry type conducting polymer actuator was prepared. Nitrile rubber (NBR) containing ionic liquid, 1-butyl-3-methyl imidazolium bis(trifluoromethyl sulfonyl)imide (BMITFSI), was utilized as the solid polymer electrolyte exhibiting high ionic conductivity as well as electrical stability. Various grades of NBRs having different amounts of acrylonitrile (ACN), viz. 23, 35 and 40 mol%, were found to be well compatible with BMITFSI. The thermomechanical property and ionic conductivity of the solid polymer electrolyte were characterized by dynamic mechanical analysis and impedance analysis, respectively. A maximum conductivity of 2.54 × 10^-4 S cm^-1 at 20 °C was achieved in the NBR sample containing 40 mol% ACN activated in BMITFSI. A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was synthesized on the surface of the solid polymer electrolyte by chemical oxidative polymerization to yield the structure of solid polymer actuator. The effect of the NBR composition on the actuation behavior was examined.