Effect of polymerization potential on the actuation of free standing poly-3,4-ethylenedioxythiophene films in a propylene carbonate electrolyte

The linear actuation of poly-3,4-ethylenedioxythiophene (PEDOT) films polymerized at different potentials (0.8–1.3 V) at −27 °C in propylene carbonate (PC) solutions of TBACF3SO3 (tetrabutylammonium trifluoromethanesulfonate) was examined under isotonic (constant force) and isometric (constant length) conditions. The actuation properties were evaluated by electrochemomechanical deformation measurements (ECDM) during cyclic voltammetry, square wave potential steps and long term cycling. The ECDM response revealed mixed ion actuation behaviour for PEDOT films polymerized at the potential extremes of 0.8 and 1.3 V. At intermediate polymerization potentials from 0.9 to 1.2 V, cation-driven actuation was observed involving immobilized triflate anions (CF3SO3−). Long term experiments (50 cycles) showed that films prepared at polymerization potentials of 0.8 V exhibited mainly anion-driven actuation, during potential steps to and from 1.0 V; conversely PEDOT prepared at a polymerization potential of 1.1 V showed exclusively cation-driven actuation. PEDOT films prepared at a polymerization potential of 1.1 V showed the maximum cation-driven actuation during cyclic voltammetry experiments including long term cycling. SEM images showed an open porous structure in all of the PEDOT films.