Active topological glass

Jan Smrek,Christos N Likos,Kurt Kremer,Iurii Chubak

doi:10.1038/s41467-019-13696-z

Jan Smrek, Christos N Likos + Show 2 more

Open Access

https://doi.org/10.1038/s41467-019-13696-z

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Abstract

The glass transition in soft matter systems is generally triggered by an increase in packing fraction or a decrease in temperature. It has been conjectured that the internal topology of the constituent particles, such as polymers, can cause glassiness too. However, the conjecture relies on immobilizing a fraction of the particles and is therefore difficult to fulfill experimentally. Here we show that in dense solutions of circular polymers containing (active) segments of increased mobility, the interplay of the activity and the topology of the polymers generates an unprecedented glassy state of matter. The active isotropic driving enhances mutual ring threading to the extent that the rings can relax only in a cooperative way, which dramatically increases relaxation times. Moreover, the observed phenomena feature similarities with the conformation and dynamics of the DNA fibre in living nuclei of higher eukaryotes.

Highlights

The glass transition in soft matter systems is generally triggered by an increase in packing fraction or a decrease in temperature
While it is known that the polymer topology has strong impact on the stress relaxation mechanism[3], it has been questioned if the topology can independently induce a glass transition[4]
Whereas many questions remain open in the traditional glass transition of passive Brownian particles, recently a whole new research direction has been opened by considering system composed of active particles that are driven by non-thermal fluctuations[10]

Summary

Introduction

The glass transition in soft matter systems is generally triggered by an increase in packing fraction or a decrease in temperature. There, a range of dynamic phenomena arises as a consequence of the competition between directed flows, characteristic for active matter in euclidean space, and the ‘hedgehog theorem’[20] that asserts the existence of topological defects in a smooth vectorial field on a sphere. In contrast to these studies, where the topology is a global property of space, here we focus on a system where the active particles themselves are not point-like but feature intrinsic circular topology, the embedding space being Euclidean with periodic boundary conditions. There is no topology involved in these models and, they are inherently different from our present work, the transition occurs due to shape changes at constant density similar to the case studied here

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