The impact of colloid-solvent dynamic coupling on the coarsening rate of colloidal phase separation

Michio Tateno; Jiaxing Yuan; Hajime Tanaka

doi:10.1016/j.jcis.2025.01.004

The impact of colloid-solvent dynamic coupling on the coarsening rate of colloidal phase separation

J Colloid Interface Sci. 2025 Jan 8;684(Pt 2):21-28. doi: 10.1016/j.jcis.2025.01.004. Online ahead of print.

Authors

Michio Tateno¹, Jiaxing Yuan², Hajime Tanaka³

Affiliations

¹ Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8904, Tokyo, Japan; Materials Research Laboratory, University of California Santa Barbara, Santa Barbara, 93106, CA, USA.
² Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8904, Tokyo, Japan.
³ Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8904, Tokyo, Japan; Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8505, Tokyo, Japan. Electronic address: tanaka@iis.u-tokyo.ac.jp.

PMID: 39817976
DOI: 10.1016/j.jcis.2025.01.004

Abstract

Phase separation, a fundamental phenomenon in both natural and industrial settings, involves the coarsening of domains over time t to reduce interfacial energy. While well-understood for simple viscous liquid mixtures, the physical laws governing coarsening dynamics in complex fluids, such as colloidal suspensions, remain unclear. Here, we investigate colloidal phase separation through particle-based simulations with and without hydrodynamic interactions (HIs). The former incorporates many-body HIs through momentum conservation, while the latter simplifies their effects into a constant friction coefficient on a particle. In cluster-forming phase separation with HIs, the domain size ℓ grows as ℓ∝t^1/3, aligning with the Brownian-coagulation mechanism. Without HIs, ℓ∝t^1/5, attributed to an improper calculation of cluster thermal diffusion. For network-forming phase separation, ℓ∝t^1/2 with HIs, while ℓ∝t^1/3 without HIs. In both cases, network coarsening is governed by the mechanical stress relaxation of the colloid-rich phase, yet with distinct mechanisms: slow solvent permeation through densely packed colloids for the former and free draining for the latter. Our results provide a clear and concise physical picture of colloid-solvent dynamic coupling via momentum conservation, offering valuable insights into the self-organization dynamics of particles like colloids, emulsions, and globular proteins suspended in a fluid.

Keywords: Coarsening law; Colloidal suspensions; Hydrodynamics; Phase separation; Viscoelasticity.