Dynamic Behaviors of Polypyrrole Actuators in Electrolyte Solution Mixed with 2-Propanol

Abstract

It has been previously reported that dynamic behaviours of polypyrrole (PPy) soft actuators were improved when they were driven in aqueous solutions of an electrolyte, lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) containing an optimised amount of 2-propanol. In this work, the influences of the potential sweep rate on electrochemical and creep strains of PPy actuators in aqueous LiTFSI electrolyte solutions with 2-propanol concentrations of 0 and 20% were investigated under the load stress of 0.3 MPa. The electrochemical strain rates in the 0% and 20% 2-propanol solution were found to be approximately 0.1% s−1 and 0.25% s−1, respectively, and they are nearly independent of the sweep rate between 10 and 25 mV s−1. These results suggest that TFSI anion penetration into the PPy films might be limited by the interactions between the PPy surface and the TFSI anions. The creep rate was more rapidly increased as time elapsed in the electrolyte solution containing 2-propanol than that in the electrolyte solution without 2-propanol, which was due to the swelling of PPy film in the electrolyte.