Dynamical properties of different models of elastic polymer rings: confirming the link between deformation and fragility

TL;DR

This study uses numerical simulations to explore how particle deformation influences the dynamics and fragility of 2D elastic polymer rings, revealing a direct link between asphericity and system fragility, and identifying conditions for anomalous super-diffusive behavior.

Contribution

It compares three models of elastic polymer rings, demonstrating the critical role of internal elasticity and out-of-equilibrium forces in complex dynamical behaviors.

Findings

System fragility correlates with particle asphericity.

Only the model with internal elasticity shows super-diffusive dynamics.

Internal elasticity and out-of-equilibrium forces induce gel-like behaviors.

Abstract

We report extensive numerical simulations of different models of 2D polymer rings with internal elasticity. We monitor the dynamical behavior of the rings as a function of the packing fraction, to address the effects of particle deformation on the collective response of the system. In particular, we compare three different models: (i) a recently investigated model [Gnan \& Zaccarelli, Nat. Phys. 15, 683 (2019)], where an inner hertzian field providing the internal elasticity acts on the monomers of the ring, (ii) the same model where the effect of such a field on the center of mass is balanced by opposite forces and (iii) a semi-flexible model where an angular potential between adjacent monomers induces strong particle deformations. By analyzing the dynamics of the three models, we find that, in all cases, there exists a direct link between the system fragility and particle asphericity. Among the three, only the first model displays anomalous dynamics in the form of a super-diffusive behavior of the mean squared displacement and of a compressed exponential relaxation of the density auto-correlation function. We show that this is due to the combination of internal elasticity and the out-of-equilibrium force self-generated by each ring, both of which are necessary ingredients to induce such peculiar behavior often observed in experiments of colloidal gels. These findings reinforce the role of particle deformation, connected to internal elasticity, in driving the dynamical response of dense soft particles.