Abstract:

The results of an extensive study of percolation to verify some theor. predictions about percolation crit. indexes for changes in static and dynamic dielec. properties of a microemulsion a a function of temp. and frequency are presented. The dynamic behavior of the microemulsions was also studied to reveal the mechanisms that are responsible for dielec. polarization of the system. The measurements were made by the time domain dielec. spectroscopy method in the frequency range 105-1010 Hz and at 10-40°. Crit. indexes for cond. and dielec. permittivity have the values s ≈ 1.2 below and t ≈ 1.9 above the percolation threshold. The value for the crit. index s is in agreement with a dynamic percolation picture. This confirms the idea that the mechanism responsible for the temp. dependence of cond. and permittivity has the same origin. The numerical value of t indicates a percolation picture above the threshold; however, it does not provide information about the nature of percolation. The data treatment for the dynamic behavior of the microemulsions was carried out in the time domain in terms of dipole correlation functions. The correlation functions exhibit complex nonexponential relaxation behavior in the percolation region and must be deconvoluted into normal modes and represented as the sum of the simple exponential exp(-t/$\tau$) and nonexponential terms exp[-(t/$\tau$)$\beta$]. The frequency scaling parameters m, p, and u, as well as the stretched parameters in the time window $\beta$, provide information about the microstructure and dynamics of the system. The anal. of their temp. dependence shows the existence of spatial, temporal, and energetic disorder assocd. with anomalous diffusion of charge carriers in the percolation clusters. From a detailed anal. of the time relaxation data spectrum, the mol. dynamic mechanism of dielec. polarization in the percolation region was suggested. [on SciFinder(R)]