Stability of polypyrrole soft actuators in ionic liquids

Abstract

Characteristics of electrochemomechanical deformation (ECMD) of polypyrrole films using ionic liquids are reported. The PPy film prepared by electrodeposition in an ionic liquid (1-Butyl-1-methylpyrrolidinium bis(trifluorometylsulfonyl)imide, BMPTFSI) was compact and high density. The other film prepared from LiTSFI/methyl benzoate and dimethyl phthalate mixed solvents was porous and low density. Both films demonstrated a stable ECMD in the ionic liquid. The strain of ECMD was 3-5% and superimposed on a creeping, showing a typical behaviour of cation movement. The Strains of ECMD in both films operated in a mixed electrolyte of BMPTFSI and propylene carbonate were enhanced up to 17- 25 %, showing anion movement. However, the large strain decreased upon several electrochemical cycles. The results were discussed in terms of swelling of the PPy film by solvents and loss of electrochemical activity.