Length scale dependence of the dynamical heterogeneities in colloidal gelation at lowvolume fraction

Abstract

Using MD simulations of a DLVO interaction potential, we present a systematic study ofthe slow dynamics in a colloidal suspension undergoing gelation. In particular we considerthe dynamical susceptibility, defined as the fluctuation of the self-intermediate scatteringfunction, as a measure of the dynamical heterogeneities. The present study allows us torationalize the strikingly different behaviors observed at low and high volume fractions,exemplified, in particular, by the strong wavevector dependence of the dynamicalheterogeneities in the dilute incipient gel. We provide a rationale for the complex dynamicsand the heterogeneities observed on approaching gelation in terms of the aggregationprocess taking place in the system. The emerging scenario suggests that the strong lengthscale dependence of the dynamical susceptibility can be taken as the distinctive sign ofcolloidal gelation at low volume fractions, with respect to the attractive and repulsive glassfound at higher densities.