Mesoscale hydrodynamics simulations of attractive rod-like colloids in shear flow

Abstract

Suspensions of rod-like colloids show in equilibrium an isotropic–nematic coexistenceregion, which depends on the strength of an attractive interaction between the rods. Westudy the behavior of this system in shear flow for various interaction strengths. A hybridsimulation approach is employed, which consists of a mesoscale particle-basedhydrodynamics technique (multi-particle collision dynamics) for the solvent and moleculardynamics simulations for the colloidal rods. The shear flow induces alignment in theinitially isotropic phase, which generated an additional free volume around each rod andcauses the densification of the isotropic phase at the expense of an erosion ofthe initially nematic phase. Furthermore, the nematic phase exhibits a collectiverotational motion. The associated rotational time decreases linearly in with increasing shear rate , and increases with increasing attraction strength between the rods. The densitydifference between these two regions at different shear rates allows us to determine thebinodal line of the phase diagram. For large applied shear rates, the difference between thephases disappears in favor of a homogeneous flow-aligned state.