Electroactivity and electromechanical actuation of polyaniline (PANI) were studied in the nonaqueous electrolyte LiClO4/propylene carbonate (PC) by optimizing PANI dopants, which were introduced using different aqueous doping acids. Use of doping acids whose anions were soluble in PC ensured PANI's high electroactivity and hence its actuation in LiClO4/PC because these dopant anions could be easily expelled into PC, enhancing further transport of electrolyte anions into and out of the polymer. Doping acids also affected the conductivity of PANI films. In choosing a suitable doping acid for electrochemistry of PANI in nonaqueous media, the solubility of the doping acid anion in the solvent should be the first consideration. The film conductivity achieved by doping with this acid will thus be as high as possible. Electrochemical impedance analysis revealed that the capacitive component of current was the major contributor to the actuation of PANI in LiClO4/PC. Solid-state bending actuators fabricated from two identical CF3SO3H-doped gilded PANI films and poly(methylmethacrylate)/PC/ethylene carbonate/LiClO4 gel electrolyte showed fast bending actuation (2.5degrees/s), even when a low voltage of 0.8 V was applied. This was believed to result from the good solubility of the doping acid anions in PC, and to the gilding of the PANI films. (C) 2003 The Electrochemical Society.