Electro-chemical operation of ionic polymer–metal composites

Currently, there is a major engineering challenge associated with ionic polymer–metal composites (IPMCs) that needs to be resolved before they can be vastly adopted in current and future engineering markets—relaxation of the IPMC actuator under a DC voltage. In this article, we rigorously discuss the potential origin of the relaxation phenomena of IPMCs that can be related to electro-chemically induced surface reactions with electrodes. Our measured voltammograms and deflection data of IPMCs revealed that the relaxation phenomena of the IPMC actuators are primarily caused by the overpotential of the surface electrodes. The overpotential values of ca. +1 V were clearly noted for many IPMC samples. We believe that the relaxation of IPMCs originate from the platinum oxide formation during actuation—a key surface reaction. The IPMC solvated with a typical ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) as a solvent, showed a larger bending, but there was no relaxation during actuation because there was no platinum oxide formation.