Understanding the Behavior of Fully Non-Toxic Polypyrrole-Gelatin and Polypyrrole-PVdF Soft Actuators with Choline Ionic Liquids

Gelatin—a material exploited for medical applications—can be used to make a fully biologically benign soft electroactive polymer actuator that provides high performance and has been shown to be harmless. In our study, these polypyrrole-gelatin trilayer actuators with choline acetate and choline isobutyrate showed the highest strain difference and highest efficiency in strain difference to charge density ratios compared to a reference system containing imidazolium-based ionic liquid and a traditional polyvinylidene fluoride (PVdF) membrane material.

As neither the relative ion sizes nor the measured parameters of the ionic liquids could explain their behavior in the actuators, molecular dynamics simulations and density functional theory calculations were conducted. Strong cation-cation clustering was found and the radial distribution functions provided further insight into the topic, showing that the cation-cation correlation peak height is a good predictor of strain difference of the actuators.