Y. Feldman et al., MECHANISM OF THE COOPERATIVE RELAXATION IN MICROEMULSIONS NEAR THE PERCOLATION-THRESHOLD, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 54(5), 1996, pp. 5420-5427
Cooperative dynamics of three-component water-oil-surfactant microemul
sions based on sodium bis(2-ethylhexyl) sulfosuccinate surfactant were
investigated near the percolation threshold. The measurements were ma
de by means of the time domain dielectric spectroscopy method in the t
emperature interval 12 degrees C-40 degrees C, including the percolati
on range. The data treatment was carried out in time domain in terms o
f the macroscopic dipole correlation functions (DCFs) related to the s
tructural and kinetic properties of the system. It is shown that the D
CF can be described by the Kohlrausch-Williams-Watts (KWW) expression
exp[-(t/tau)(nu)] (where tau is the relaxation time and nu is the stre
tched parameter), reflecting the peculiarities of the dipole interacti
ons in a self-similar medium. For a physical interpretation of the phe
nomenological parameters tau and nu, a generalization of the known mod
el of the cooperative relaxation was made. The model developed was adj
usted for a description of the relaxation in microemulsions that have
a fractal nature in the percolation region. The results obtained testi
fy that parameters tau and nu in the KWW function are related to the s
tructure of the system and reflect the cooperative behavior of microem
ulsion droplets near the percolation threshold. It was shown also that
the macroscopic law of the relaxation of the KWW type is insensitive
to the microscopic details of charge transport in the system and that
there is a limited temporal range for the applicability of the stretch
ed law of relaxation in time domain. In order to extend the initial te
mporal interval of the applicability of the relaxation function the co
rrelation to the KWW term was found.