Polyaniline actuators

Actuation of polyaniline (PANI)/Au bending bilayers and stretched polyaniline fibers doped with 2-acrylamido-2-methyl-propane-1-sulfonic acid was studied in aqueous methanesulfonic acid. Electrochemical activity was retained even upon repeated cycling into the pernigraniline state, unlike in HCl. The polyaniline expanded 1.6% from the leucoemeraldine state to the emeraldine state, similar to the strain in HCl, and then contracted 0.2% upon entering the pernigraniline state. The polyaniline was not mechanically stable in the pernigraniline state, however: the ultimate tensile strength decreased so much that the actuators were rendered ineffective for lifting a load. In addition, in this electrolyte the creep was considerable even under small loads; the Young's modulus was only 0.4 GPa in the oxidized state, compared to 1.7 GPa in HCl.