The Importance of Oscillatory Structural Forces in the Sedimentation of a Binary Hard-Sphere Colloidal Suspension

Abstract

Concentrated colloidal dispersions are complex systems comprised of colloidal particles of various sizes. This paper summarizes recent experimental and theoretical findings on understanding the interactions between microspheres in the presence of submicrometer particles; the submicrometer particles can be solvent molecules, surfactant micelles, or other nanometer-sized particles. In a hard-sphere suspension containing microspheres in the presence of submicrometer particles, oscillatory structural (entropic) forces between large particles, caused by small particles, arise as a result of the collective particle−particle interactions. The magnitude of the oscillatory structural forces is theoretically estimated based on the statistical mechanics approach, Monte Carlo simulations, and stochastic particle dynamics methods. Also, sedimentation experiments using spherical low-charged, binary hard-sphere particle suspensions with a large size ratio are presented to elucidate the importance of the oscillatory stru...