[SY-H2] Elastic properties and effective interactions of in silico realistic microgels
The bulk behaviour of colloidal suspensions depends crucially on the microscopic details of the particle-particle interaction[1]. For polymer-based building blocks, the interactions depend on a large number of parameters such as the particle microstructure, its composition and related physico-chemical properties (solvophobicity, charge density, etc.). Among the huge variety of available systems, stimuli-responsive microparticles built out of polymer networks, so-called microgels, have emerged as one of the most interesting class of soft particles, for both a theoretical and applicative standpoint[2].
Here we build upon a recently-developed method[3] to generate and simulate realistic in silico microgels. We first look at the single-particle mechanics by calculating the elastic moduli in the small-deformations regime. We then use Umbrella Sampling and a generalised Widom insertion method to accurately estimate the two-body effective interaction.
We show for the first time that the Hertzian theory works well for large separations, and that in this regime the single-particle elastic moduli can predict the amplitude of V(r) for a wide range of network topologies. However, for smaller separations the two microgels start to strongly interact and change their shape and V(r) deviates from the predicted Hertzian behaviour.
This work establishes a clear link between the microscopic network properties and the resulting microgel-microgel interactions, paving the way for a deeper understanding of the bulk behaviour of microgel suspensions.
[1] C. N. Likos, Phys. Rep., 348, 267 (2001)
[2] A. Fernandez-Nieves, H. Wyss, J. Mattsson, D. A. Weitz, Microgel Suspensions: Fundamentals and Applications; John Wiley & Sons (2011)
[3] N. Gnan, L. Rovigatti, M. Bergman, E. Zaccarelli, Macromolecules, 50, 8777 (2017)
Here we build upon a recently-developed method[3] to generate and simulate realistic in silico microgels. We first look at the single-particle mechanics by calculating the elastic moduli in the small-deformations regime. We then use Umbrella Sampling and a generalised Widom insertion method to accurately estimate the two-body effective interaction.
We show for the first time that the Hertzian theory works well for large separations, and that in this regime the single-particle elastic moduli can predict the amplitude of V(r) for a wide range of network topologies. However, for smaller separations the two microgels start to strongly interact and change their shape and V(r) deviates from the predicted Hertzian behaviour.
This work establishes a clear link between the microscopic network properties and the resulting microgel-microgel interactions, paving the way for a deeper understanding of the bulk behaviour of microgel suspensions.
[1] C. N. Likos, Phys. Rep., 348, 267 (2001)
[2] A. Fernandez-Nieves, H. Wyss, J. Mattsson, D. A. Weitz, Microgel Suspensions: Fundamentals and Applications; John Wiley & Sons (2011)
[3] N. Gnan, L. Rovigatti, M. Bergman, E. Zaccarelli, Macromolecules, 50, 8777 (2017)