The effects of adding ionic liquids to plasticized PVC gel actuators

Four ionic liquids (ILs), trihexyl (tetradecyl) phosphonium methanesulfonate ([mes^-]), trihexyl (tetradecyl) phosphonium dodecylbenzenesulfonate ([dbs^-]), trihexyl (tetradecyl) phosphonium chloride([Cl^-]) and tetrabutyl phosphonium methanesulfonate ([tbt⁺]), were chosen to add to plasticized poly(vinyl chloride) (PVC) gels for improving actuation behavior at low electric fields. It was found that the IL trihexyl (tetradecyl) phosphonium chloride ([Cl^-]) is best matched to PVC gels, and the amount of IL is an important factor for PVC gel actuation. With less than 0.01 wt% of IL the PVC gel can actuate similarly to the gel without IL, but less than half of the DC voltage is required. It was also found that PVC gel with a minute quantity of IL not only maintained the deformation properties of the PVC gel without IL, but also enhanced the dielectric constant and decreased the interfacial resistance. However, increasing the amount of IL from 0.01 to 0.02 wt% resulted in one way bending and delayed recovery response, while more than 0.02 wt% resulted in almost no actuation response. The reason for these observations was confirmed as being accumulation of electric charges in the PVC gel interior with increased IL content. The accumulated ionic liquid resists migration of electric charges and causes smaller deformation or recovery response.