(525g) Rheology of Janus Particle Suspensions Via Brownian Dynamics Simulation

Recent experimental and theoretical studies on the suspension of patchy or Janus colloidal particles have examined collective structures, phase diagrams, and self-assembly at different times scales and particle concentrations. However, only a few efforts have focused on understanding their potential rheological advantages in comparison to their isotropic counterparts. In order to make some progress in this field, we propose a simple model consisting of Janus particles immersed in a Newtonian fluid interacting via a combination of square-well (SW) and hard-sphere (HS) surface potentials and in the absence of hydrodynamic interactions. Using Brownian dynamics simulation, the osmotic pressure, the effective viscosity, and normal stress differences are obtained at equilibrium and away from it, by varying the Péclet number -- the ratio between shear and Brownian forces -- and particle volume fraction. To provide a better description of the microstructure of the suspension and explain the time-dependent rheological properties, we characterize at each time interval the number of clusters, the number of particles in each cluster, the radius of gyration, and the cluster effective size. The results are compared to isotropic suspensions interacting with only HS or SW potentials.