Abstract
AbstractThe complex permittivity ϵ = ϵ′ −j ϵ″ of polypyrrole (PPY) samples and polypyrrole–poly(methyl methacrylate) (PPY‐PMMA) composites is calculated from measurements in the radiofrequency and microwave range (F = 103–8 × 109 Hz) at room temperature. A relaxation phenomenon is observed in PPY‐PMMA composites with polypyrrole concentration p = 6–12% by weight. The frequency Fmax corresponding to the maximum of ϵ″ appears in the radiofrequency domain and increases with the PPY concentration from 104 to 2 × 106 Hz. This relaxation is caused by space charge moving into the conductive clusters of PPY. At low frequency F ≪ Fmax, the real part of the permittivity ϵ′ becomes very high. For F ≪ Fmax, PPY‐PMMA composites have a percolative behaviour, the percolation threshold pc being 3.85%. For F ≫ Fmax, in the microwave domain, an ac component of the conductivity σac appears. σac varies as a power function of the frequency, σac ∝ ω x; with x < 1, x independent of p.© 2001 Society of Chemical Industry
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