Non-exponential dynamics in the microemulsions near the percolation threshold from time domain dielectric spectroscopy

A percolation phenomenon is found in microemulsions when the water fraction, the temperature, the pressure, or the ratio of water to the surfactant was varied. Below the percolation onset, where the microemulsion has a structure of spherical droplets, the main contribution in the relaxation mechanism comes from the fast relaxation processes with characteristic relaxation times less than 1 ns. The processes are inherent to the dynamics of the single droplet components. In the percolation region transient clusters of a fractal nature are formed because of attractive interactions between droplets. An interpretation of the results was done in the framework of the dynamic percolation model. According to this model, near the percolation threshold, in addition to the fast relaxation related to the dynamics of droplet components, there are at least two much longer characteristic time scales. The longest process has characteristic relaxation times greater than a few microseconds and should be associated with the rearrangements of the typical percolation cluster. The temporal window of the intermediate process is a function of temperature. This intermediate process reflects the cooperative relaxation phenomenon associated with the transport of charge carriers along the percolation cluster. The purpose of this work is to further investigate the fractal dynamics of this cooperative relaxation process in microemulsions near the percolation threshold.