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We report on a series of static and dynamic light-scattering experiments performed in a three-component water-in-oil microemulsion consisting of water/decane/AOT (sodium-di-2-ethyl hexyl sulfosuccinate). The measurements have been done throughout the isotropic one-phase region, in a large domain of volume fractions, as a function of temperature and scattering wave vector. For volume fractions φ > 0.42 the long-time tail of the droplet density correlation function S(Q t) is not an exponential, but tends toward a stretched exponential. The temperature and wave vector dependences of the first cumulant K1, and of the average relaxation time have bene investigated. These parameters change abruptly when crossing the well-defined electrical percolation locus. A theoretical model based on the aggregation of polydispersed fractal clusters of fractal dimension d=2, is in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

A three-component microemulsion system consisting of mixtures of water, decane, and a surfactant AOT (WDA), has been studied by means of extensive light scattering measurements, including the intensity, turbidity and linewidth. The measurements have been performed in the one-phase region over a very large temperature range, along the critical and several off-critical constant microemulsion droplet volume fractions. The standard theory of critical binary fluids, complemented by the linear model equation of state, accounts very well for the intensity data in the vicinity of the lower phase separation temperature Tp using a single value for the short range correlation length, ξ0=(13.5±1.5) Å. We have also been able to fit the dynamic light scatteirng dat by combining a mode-coupling theory including the background effects, and the critical equations of state using a cutoff wavelength qD−1 equal to the constant average diameter of microemulsion droplets. Moreover, we find clear evidence for a crossover from critical to single particle behavior in both static and dynamic light scattering data. A cropssover temperature Tx has been identified for ξ(Tx)=qD−1 so that qD, which can only be measured far away from Tp, plays the most important part in controlling the critical dynamics in the whole temperature range. [ABSTRACT FROM AUTHOR]