Topological Linking Drives Anomalous Thickening of Ring Polymers in Weak Extensional Flows

Abstract

Molecular dynamics simulations confirm recent extensional flow experiments showing ring polymer melts exhibit strong extension-rate thickening of the viscosity at Weissenberg numbers W i << 1. Thickening coincides with the extreme elongation of a minority population of rings that grows with W i. The large susceptibility of some rings to extend is due to a flow-driven formation of topological links that connect multiple rings into supramolecular chains. Links form spontaneously with a longer delay at lower W i and are pulled tight and stabilized by the flow. Once linked, these composite objects experience larger drag forces than individual rings, driving their strong elongation. The fraction of linked rings depends non-monotonically on W i, increasing to a maximum when W i ∼ 1 before rapidly decreasing when the strain rate approaches 1/τe. arXiv:1910.14666v1 [cond-mat.soft]

Active topological glass

“…We suspect, that such threadings could also be relevant in the dramatic increase of the viscosity in stretched untangled melt of rings 48 (after this paper has been already accepted, the hypothesis has been confirmed in ref. 49 ). To prove at least that ring topology and threadings are essential for the glass transition, we took a configuration of the system in the glassy state and cut the bond connecting two cold monomers in the middle of the cold segment on each ring.…”

Stretching of Bombyx mori Silk Protein in Flow

“…This view of silk registration is highly idealised, in particular because associating polymers exhibit a broad stretch distribution in steady-state flow. Indeed, akin to ring polymers [ 55 , 56 ], rare events of large chain stretches emerge below the stretch transition. We speculate that the width of the distribution determines how likely it is for equally stretched polymers to associate with each other, such that a correlated ‘registered’ network may form.…”

Topological and threading effects in polydisperse ring polymer solutions

“…In dense systems, the so-called threading conformations, where one polymer segment is intersecting the loop opening of another, slow down the polymer diffusive dynamics. Such threading events are correlated with a slower dynamics of equilibrium systems of rings [9,10], significantly impact viscosity when the rings are long [11] or when the threadings are enhanced by outof-equilibrium conditions [12,13]. The threadings form a particular subset of the topologically allowed conformations and therefore we investigate how they impact the effective interaction potential in general and its topological part in particular.…”