Polypyrrole Films with Anisotropy for Artificial Muscles and Examination of Bending Behavior

The novel features of electrochemical actuators fabricated from a cylindrical polypyrrole (PPy) pipe prepared by the electrochemical polymerization technique have been described. This cylindrical PPy pipe was cut into a rectangular film and its electrochemical and electrical properties were measured. When the inner surface of the PPy film (surface in contact with electrolyte when PPy was polymerized) was insulated and redox was carried out, the PPy film bent toward the outer surface (surface in contact with a slender Teflon pipe when PPy was polymerized) upon reduction and returned to its original shape upon oxidation. However, the bending was not completely accomplished by redox when the outer wall side of the PPy film was insulated. Although such an anomalous bending in the PPy-film actuator cannot be explained satisfactorily at this stage, we speculate that the bending phenomena are due to the difficulty of dopant transfer between inner and outer surfaces.