PEDOT and PPy conducting polymer bilayer and trilayer actuators

Actuators based on conducting polymers are attracting increasing interest due to their desirable features such as large mechanical stress generated, sufficient maximum strain values, high reversibility, good safety properties and the possibility of precise control using small voltages. Many attempts have been made to improve the actuator performance. We report electromechanical measurements on actuators of bilayer and trilayer free standing films prepared with polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymers. Both types of conducting polymer are pre-doped during synthesis with dodecyl benzenesulfonate (DBS). These multilayer films were prepared electrochemically so that the PEDOT layer is very thin compared to that of the PPy layer. In the trilayer film, the PEDOT layer is sandwiched between two PPy layers.The films were characterized electromechanically and the results compared with those of PPy single layer film. Bilayer films show a significant increase in the strain measured at higher scan rates (>100 mV s−1). The force difference generated between the reduced and oxidized states is much higher for trilayer films and higher for bilayer films than that in a single layer of PPy. Trilayer films are both stronger and faster than a single layer PPy film of half the thickness.