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

Electro-chemomechanical expansion and contraction in polypyrrole films synt hesized electrochemically from pyrrole in electrolytes of p-phenolsulfonic (PPS) acid has been measured directly in various supporting electrolytes. I t 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 redu ced and oxidized states studied under the present conditions. The electro-c hemomechanical expansion of polypyrrole films is primarily driven by the in sertion of bulky ions, regardless of oxidation and reduction. This is diffe rent from the mechanism of polyaniline films, in which a conformation chang e of the polymer structure is involved. The mechanism of electro-chemomecha nical deformation in polypyrrole film is discussed, taking the conductivity and conformation of polypyrrole into consideration.