Dynamic slowing-down in dense microemulsions near the percolation threshold

We review a series of investigations of the static and dynamic properties of a three‐component water‐in‐oil microemulsion system in which the molar ratio of water to surfactant is kept constant. This system behaves effectively like a two‐domponent macromolecular fluid in which there are spherical, surfactant coated water droplets of macroscopic dimensions dispersed in a continuum of oil. The properties investigated include electrical conductivity, dielectric relaxation, shear viscosity and viscoelastic relaxation, static neutron and light scattering and dynamic light scattering. We focus mainly on the phenomena of the dynamic slowing‐down of the dielectric relaxation and the droplet density fluctuations as the system approaches the percolation threshold from below, both in temperature and in volume fraction. A theory of static and dynamic light scattering, formulated along the lines of scattering from a system of polydisperse fractal clusters, quantitatively accounts for the dynamic slowing‐down phenomenon and the non‐exponential decay of the time correlation function.