Electrochemistry of surfactant-doped polypyrrole film(I): Formation of columnar structure by electropolymerization
- Tokyo Univ. of Agriculture and Technology (Japan)
- Japan Women`s Univ., Tokyo (Japan)
Electroactive polypyrrole (PPy) films have been studied widely in the field of applied material science for high energy/power storage applications. Perpendicularly oriented columnar structure was obtained for electropolymerized polypyrrole films formed from micellar solution of anionic surfactants. The surfactants used as dopants were a class of anionic surfactant, namely, Na salts of dodecyl sulfate (SDS) and dodecylbenzene sulfonate (SDBS). The formation process of polypyrrole films on electrode surfaces was studied with in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods to monitor the structure of the grown polymers. In EQCM measurement, the frequency shift ({Delta}f) and the resonance resistance ({Delta}R) of the quartz crystal electrode were obtained simultaneously. An abrupt increase in {Delta}R was observed for both PPy/DS and PPy/DBS films at about 60--100mC/cm{sup 2}. Such a drastic change in {Delta}R, which may be associated with the emergence of the viscoelastic properties of the films, could be explained by the formation of columnar structure. In situ AFM observation clearly indicated that such a structure started to form around these critical charges. The cyclic voltammograms for the PPy/DS and PPy/DBS{sup {minus}} films showed sharp redox couples observed around {minus}0.5 to 0.6 V. The diffusion rate of cations for the resulting films was studied with ac impedance measurement as a function of the concentration of surfactant dopants. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. 3 orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a special formation process of polypyrrole in micelle solution: the mechanism is discussed here.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 61497
- Journal Information:
- Journal of the Electrochemical Society, Vol. 142, Issue 2; Other Information: PBD: Feb 1995
- Country of Publication:
- United States
- Language:
- English
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