Dynamic Slowing-Down and Nonexponential Decay of the Density Correlation Function in Dense Microemulsions

Abstract

Quasielastic-light-scattering measurements were made on microemulsions in which the apparent volume fraction $\ensuremath{\varphi}$ of the microemulsion droplets was varied from 0.1 to 0.75. The density correlation function shows an exponential decay at short time but deviates from it at long time especially for intermediate $\ensuremath{\varphi}$. The initial decay rates of the correlation functions decrease steadily as a function of $\ensuremath{\varphi}$, reaching a minimum at ${\ensuremath{\varphi}}_{c}=0.62$, and increase thereafter. The overall time dependence of the correlation functions can be fitted by the function $\mathrm{exp}[\ensuremath{-}{(\frac{t}{T})}^{\ensuremath{\alpha}}]$; the exponent $\ensuremath{\alpha}$ varies from 1 down to 0.66 and back up again to 0.9 over the range of $\ensuremath{\varphi}$.