Length scale dependence of dynamical heterogeneity in a colloidal fractal gel

Abstract

We use time-resolved dynamic light scattering to investigate the slow dynamics of a colloidal gel. The final decay of the average intensity autocorrelation function is well described by $g\_2(q,\tau )-1\sim \exp [-(\tau /\tau \_\mathrm{f}{)}^p]$, with $\tau \_\mathrm{f}\sim q^{-1}$ and $p$ decreasing from 1.5 to 1 with increasing $q$. We show that the dynamics is not due to a continuous ballistic process, as proposed in previous works, but rather to rare, intermittent rearrangements. We quantify the dynamical fluctuations resulting from intermittency by means of the variance $\chi (\tau ,q)$ of the instantaneous autocorrelation function, the analogous of the dynamical susceptibility $\chi \_4$ studied in glass formers. The amplitude of $\chi$ is found to grow linearly with $q$. We propose a simple --yet general-- model of intermittent dynamics that accounts for the $q$ dependence of both the average correlation functions and $\chi$.

Revised and improved, to appear in Europhys. Lett

References in corpus (1)

• Time Resolved Correlation measurements of temporally heterogeneous dynamics

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