Electrochemomechanical Deformation of Polyaniline Films

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Abstract
The deformation of unstretched and stretched polyaniline (PANI) films by the electrochemical cycle has been studied. An anisotropic deformation is observed. The largest expansion and contraction upon oxidation and reduction, respectively, are observed for the direction perpendicular to the draw axis. The deformation parallel to the draw axis is the smallest for oxidation leucoemeraldine salt to emeraldine salt (ES), and shows even slight contraction upon oxidation from ES to pernigraniline salt. The expansion ratio Δℓ/ ℓ0, where Δℓ is the increment of expansion and ℓ0 is the original length, is found to be proportional to the degree of oxidation. In the unstretched film, Δℓ/ ℓ0 is about -2% at 20% reduction from the ES state. The results are discussed in terms of intercalation of dopant ions per repeating unit between chains and the conformational change of chains.