Influence of Topology on Rheological Properties of Polymer Ring Melts

TL;DR

This study uses numerical simulations to explore how the topology and stiffness of polymer rings affect their flow properties, revealing significant differences in viscosity based on knotting and concatenation, with potential applications in polymer separation.

Contribution

It provides new insights into how topology influences rheological behavior of polymer melts, especially regarding knots and catenanes, which was less understood before.

Findings

Knotted oligomer rings are more viscous than unknotted ones at high shear rates.

Concatenated rings (catenanes) are consistently more viscous than unconcatenated rings.

Topology-based rheological differences can be used for polymer separation in microfluidic devices.

Abstract

We investigate with numerical simulations the influence of topology and stiffness on macroscopic rheological properties of polymer melts consisting of unknotted, knotted or concatenated rings. While melts of flexible, knotted oligomer rings tend to be significantly more viscous than their unknotted counterparts, differences vanish in a low shear rate scenario with increasing degree of polymerization. Melts of catenanes consisting of two rings on the other hand are consistently more viscous than their unconcatenated counterparts. These topology-based differences in rheological properties can be exploited to segregate mixtures of otherwise chemically similar polymers, e.g., in microfluidic devices, which is demonstrated by exposing a blend of flexible knotted and unknotted oligomer rings to channel flow.