Shear thinning of suspensions of sterically stabilized spheres studied by Stokesian dynamics simulations

Abstract

Stokesian dynamics simulations are presented of suspensions of sterically stabilized spheres in a viscous medium, subjected to simple shear. The steric repulsion between the grafted polymer layers of different particles is modeled using an interaction potential that is calculated using a self-consistent field lattice theory. The shear rate dependence and the volume fraction dependence of the suspension viscosity are calculated and compared to experimental data [Nommensen et al. Phys. Rev. E 59, 3147 (1999)]. It is found that shear thinning is mainly caused by the interaction contribution to the viscosity. The present paper, combined with a recent paper of Nommensen et al. [Langmuir 16, 1902 (2000)], shows that computer simulations, theoretical analysis, and experimental work give a consistent physical picture of the rheology of these suspensions when the proper interaction potential is used.

Algorithms for Particle-Field Simulations with Collisions

“…We do not maintain that our approach is suitable for all applications involving particles immersed in a fluid. For instance, the Navier-Stokes equation for solid particles in a liquid gives rise to existence of squeeze and shear lubrication forces which demands a different numerical solution procedure [15,16].…”

Dynamics of permeable particles in concentrated suspensions

“…Examples are fuzzy-sphere systems consisting of highly porous, cross-linked microgel spheres exhibiting large volume changes as a function of temperature [1,2]. Another experimentally well-studied class of permeable colloids are core-shell-like particles consisting of an impermeable rigid core and a permeable stabilizing layer of some soft material [3,4], such as grafted polymers [5,6]. Despite the importance of permeable particles both from a fundamental viewpoint and in terms of applications, little is known theoretically about transport properties in non-dilute systems, such as self-and collective diffusion coefficients.…”

Manifestation of Polyacrylamide Inverse-Emulsion Instabilities through Oscillatory Shear

“…These results indicate that the greater hydrophobic chain length (115 Å) of the ABA triblock copolymeric stabilizer compared to the 20 Å of the standard fatty acid chains enhanced the interparticle interactions. By increasing the level of ABA block copolymeric stabilizer in the blend, long-range interactions were expected to dominate, such that the viscosity increase resulted from the enhancement of structural linkages . Confirmation of this hypothesis can be obtained from the elastic modulus, which reflects interparticle interactions .…”