Modelling the rheology of anisotropic particles adsorbed on a two-dimensional fluid interface

• Published in: Soft matter Vol. 11; no. 22; pp. 4383 - 4395
• Main Authors: Luo, Alan M, Sagis, Leonard M. C, Öttinger, Hans Christian, De Michele, Cristiano, Ilg, Patrick
• Format: Journal Article
• Language: English
• Published: England 14.06.2015
• Subjects: Anisotropy; capillary interactions; complex fluids; Computer simulation; constitutive equation; Constitutive equations; Constitutive relationships; Dynamical systems; dynamics; Ellipsoids; emulsions; general formalism; liquid-crystals; Mathematical models; Rheology; Shear; thermodynamics
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c5sm00372e

We present a general approach based on nonequilibrium thermodynamics for bridging the gap between a well-defined microscopic model and the macroscopic rheology of particle-stabilised interfaces. Our approach is illustrated by starting with a microscopic model of hard ellipsoids confined to a planar surface, which is intended to simply represent a particle-stabilised fluid-fluid interface. More complex microscopic models can be readily handled using the methods outlined in this paper. From the aforementioned microscopic starting point, we obtain the macroscopic, constitutive equations using a combination of systematic coarse-graining, computer experiments and Hamiltonian dynamics. Exemplary numerical solutions of the constitutive equations are given for a variety of experimentally relevant flow situations to explore the rheological behaviour of our model. In particular, we calculate the shear and dilatational moduli of the interface over a wide range of surface coverages, ranging from the dilute isotropic regime, to the concentrated nematic regime. We link the structure of a particle-stabilised fluid-fluid interface with rheological behaviour. Here we show the response of the interface to oscillatory dilatational flow.