Factors Affecting Electromechanical Properties of Ionic Polymer Actuators Based on Ionic Liquid-Containing Sulfonated Block Copolymers

Abstract

We investigate the electromechanical properties of ionic polymer actuators based on sulfonated block copolymers and imidazolium ionic liquids (ILs) to unveil key factors affecting the actuation performance. First, the extent of electromechanical deformation of the actuators was proven to be largely affected by the type of anion in the ILs, as understood by the anion-dependent ionic conductivity, charging time, and Young’s modulus of IL-containing polymers. In particular, upon switching the anion from hexafluorophosphate to bis(trifluoromethane)sulfonimide, more than a 2-fold enhancement in the bending strain was observed, which has not been previously reported. Second, we show that the bending strain and durability of the actuators are tunable in a straightforward manner by controlling the block architecture and molecular weight of the polymer, where the use of triblock copolymers was found to be beneficial in enhancing the actuation performance. The high mechanical strength of IL-containing triblock copo...