Colloidal aggregation and dynamics in anisotropic fluids

We present experiments and numerical simulations to investigate the collective behavior of submicrometer-sized particles immersed in a nematicmicellar solution. We use latex sphereswith diameters ranging from 190 to 780 nm and study their aggregation properties due to the interplay of the various colloidal forces atwork in the system.Wefound that the morphology of aggregates strongly depends on the particle size, with evidence for two distinct regimes: the biggest inclusions clump together within minutes into either compact clusters or V-like structures that are completely consistent with attractive elastic interactions. On the contrary, the smallest particles form chains elongated along the nematic axis, within comparable timescales. In this regime, Monte Carlo simulations, based on a modified diffusion-limited cluster aggregation model, strongly suggest that the anisotropic rotational Brownian motion of the clusters combined with short-range depletion interactions dominate the system coarsening; elastic interactions no longer prevail