ELECTROCHEMICAL IMPEDANCE MEASUREMENTS OF P-DOPED POLYACETYLENE IN LIGACL4-CH3NO2 MEDIUM

Impedance measurements have been carried out on new oriented polyacetylene during electrochemical intercalation in a LiGaCl4CH3NO2 medium. The electrocapillary approach of the intercalation process into pyrographite, a well-defined host material, is extrapolated to polyacetylene. Results are discussed on the basis of galvanostatic, cyclic voltammetry and a.c. impedance measurements. In the case of a constant current charge of polyacetylene, it is seen that Nyquist diagrams obtained for different dopant concentrations (y) are typical of the capacitive behaviour of a blocking porous electrode. We can conclude that intercalation into polyacetylene is mainly a capacitive process: for 0 < y ≤ 0.02, the measured capacity varies with the ratio doped (CH)x/undoped (CH)x; for 0.02 < y < 0.05, the capacity of the electrode remains constant although X-ray studies show that the sample is a mixture of pristine and doped (CH)x. The low-frequency internal capacitance is thus related to the diffusion of the intercalated species through the external doped part of the fibrils. © 1990.