Hydrodynamic modes and topology in microemulsions and L3 phases

Abstract

We estimate the decay rates for surfactant and oil/water long-wavelength concentration fluctuations in phases of random fluid films, such as microemulsions and « sponge » L3 phases. We consider the effects of two (possibly long) microscopic time scales : one for local relaxation of the film topology, and one for relaxation of the relative volumes of the two regions partitioned by the film (when this is not conserved). These effects may be observable in dynamic light scattering, temperature jump and magnetic birefringence studies. For dilute SDS/dodecane/pentanol/H2O sponge phases we use experimental data to estimate bounds for the topological relaxation time, and find this to be of order 0.01 s