Mixed-ion linear actuation of PPy and PEDOT in propylene carbonate-triflate electrolytes

Investigations of the actuation properties of free standing PPy and PEDOT films in a propylene carbonate-triflate electrolyte (PC/TBACF3SO3) under isotonic (constant load) conditions are presented in this work. The PPy film showed mixed ion movement during charging and discharging in cyclic voltammetric and chronoamperometric experiments. At a potential of -1.0 V the maximum strain was in the range of 1-2 % whereas at the anodic potential of +1.0 V strains in the range of 3-4 % were observed. Cyclic voltammetry experiments at higher scan rates to 10 mV/s led to a decrease in the anodic strain and an increase in the cathodic strain before it declined at higher scan rates. The free-standing PEDOT films showed mainly cathodic actuation at the potential -1.0 V and the size of actuation was again dependent upon the scan rate. Cation movement is discussed in terms of the immobilisation of CF3SO3- anions during polymerisation. Extended potential step experiments showed good actuation and low creep in the potential range between 0.0 and +1.0 V. The surface morphology (SEM) showed an open porous structure for PEDOT in contrast to the smooth morphology of PPy.