Critical dynamics of supramolecular mixtures. Application to microemulsion systems and to nonionic amphiphile-water micellar solutions

We discuss the static and dynamic critical behavior of binary solutions of water with some alkyl-oxyethylene-glycol monoether (CiEj) and of di 2 ethylhexyl sodium sulfosuccinate (AOT)-water-decane ternary microemulsion systems. Extensive sets of measurements of the scattered light intensity, of the order-parameter fluctuations time correlation function, and of the shear viscosity, have been performed for different systems. In most of the cases our data sets show systematic deviations from the behavior usually observed for molecular binary fluids. We show that generalized hydrodynamics cannot account for these deviations. A modified version of the Sorensen et al. (1976) dynamical droplet model has been worked out. This model which assumes that the physical clusters formed close to the critical point can be treated like percolating aggregates, and which includes the finite size of the monomers, very well accounts for all our experimental results.