Mixed-ion linear actuation behaviour of polypyrrole

The linear actuation of polypyrrole (PPy) films polymerized at 0.85 V (versus Ag-wire) and −27 °C in propylene carbonate solutions of tetrabutylammonium trifluoromethanesulfonate (TBACF₃SO₃) was investigated in the same monomer-free electrolyte. The actuation properties were evaluated by electrochemomechanical deformation measurements (ECMD) during cyclic voltammetry and potential step experiments. The ECMD response revealed mixed-ion actuation behaviour for the film, namely the polymer film actuation was dominated by cation movement at potentials less than 0 V and anion movement at potentials greater than 0 V, with film lengthening seen at both potential extremes. It was found that the ratio of cathodic to anodic actuation can be modulated by the scan rate. Longer-term actuation (50 potential steps from −1 V to 0 V, or from 0 V to +1 V), indicated better film stability when cycled in the anodic region. Changing the electropolymerisation potential to a higher value of 1.2 V led to a modification in ECMD characteristics for the PPy/CF₃SO₃ films.