Direct measurement and mechanism of electro-chemomechanical expansion and contraction in polypyrrole films

Electro-chemomechanical expansion and contraction in polypyrrole films synthesized electrochemically from pyrrole in electrolytes of p-phenolsulfonic (PPS) acid has been measured directly in various supporting electrolytes. It is found that the films maintain a high electro-chemomechanical activity and conductivity in the wide pH range from pH4 to pH10 and also at the reduced and oxidized states studied under the present conditions. The electro-chemomechanical expansion of polypyrrole films is primarily driven by the insertion of bulky ions, regardless of oxidation and reduction. This is different from the mechanism of polyaniline films, in which a conformation change of the polymer structure is involved. The mechanism of electro-chemomechanical deformation in polypyrrole film is discussed, taking the conductivity and conformation of polypyrrole into consideration.