Dynamics of a suspension of interacting yolk-shell particles

¹ Biology and Soft Matter Division, Oak Ridge National Laboratory - Oak Ridge, TN 37831, USA
² Instituto de Física “Manuel Sandoval Vallarta”, Universidad Autónoma de San Luis Potosí Álvaro Obregón 64, 78000 San Luis Potosí, SLP, México

Received: 22 September 2014
Accepted: 8 December 2014

Abstract

In this work we study the self-diffusion properties of a liquid of hollow spherical particles (shells) bearing a smaller solid sphere in their interior (yolks). We model this system using purely repulsive hard-body interactions between all (shell and yolk) particles, but assume the presence of a background ideal solvent such that all the particles execute free Brownian motion between collisions, characterized by short-time self-diffusion coefficients for the shells and for the yolks. Using a softened version of these interparticle potentials we perform Brownian dynamics simulations to determine the mean squared displacement and intermediate scattering function of the yolk-shell complex. These results can be understood in terms of a set of effective Langevin equations for the N interacting shell particles, pre-averaged over the yolks' degrees of freedom, from which an approximate self-consistent description of the simulated self-diffusion properties can be derived. Here we compare the theoretical and simulated results between them, and with the results for the same system in the absence of yolks. We find that the yolks, which have no effect on the shell-shell static structure, influence the dynamic properties in a predictable manner, fully captured by the theory.