The microscopic role of deformation in the dynamics of soft colloids

TL;DR

This study introduces a new model of soft colloids with internal elasticity to investigate how particle deformation influences their dynamics at high densities, revealing complex behaviors and the importance of softness.

Contribution

The paper presents a novel polymer ring model incorporating particle deformation, bridging the gap between experimental observations and previous simple simulation models.

Findings

Compressed exponential decay of scattering functions at high density

Super-diffusive behavior of mean-squared displacement

Relaxation times vary significantly with particle softness

Abstract

Soft colloids allow to explore high density states well beyond random close packing. An important open question is whether softness controls the dynamics under these dense conditions. While experimental works reported conflicting results, numerical studies so far mostly focused on simple models that allow particles to overlap, but neglect particle deformations, thus making the concept of softness in simulations and in experiments very different. To fill this gap here we propose a new model system consisting of polymer rings with internal elasticity. At high packing fractions the system displays a compressed exponential decay of the intermediate scattering functions and a super-diffusive behavior of the mean-squared displacement. These intriguing features are explained in terms of the complex interplay between particle deformations and dynamic heterogeneities, which give rise to persistent motion of ballistic particles. We also observe a striking variation of the relaxation times with increasing particle softness clearly demonstrating the crucial role of particle deformation in the dynamics of realistic soft colloids.