Abstract
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 T p using a single value for the short range correlation length, ξ 0=(13.5±1.5) A. 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 q D −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 T x has been identified for ξ(T x )=q D −1 so that q D , which can only be measured far away from T p , plays the most important part in controlling the critical dynamics in the whole temperature range.
Published Version
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