2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D12: Out-of-Equilibrium: Structure and Dynamics of Polymers
3:00 PM–6:00 PM,
Monday, March 6, 2023
Room: Room 235
Sponsoring
Unit:
DPOLY
Chair: Yangyang Wang, Oak Ridge National Laboratory; Shiwang Cheng, Michigan State University
Abstract: D12.00002 : Single Polymer Dynamics of Ring-Linear Blends and Entangled Solutions
3:36 PM–4:12 PM
Abstract
Presenter:
Charles M Schroeder
(University of Illinois at Urbana-Champaign)
Author:
Charles M Schroeder
(University of Illinois at Urbana-Champaign)
Single polymer dynamics provides a powerful window to directly view the nonequilibrium behavior of polymers in flow. In recent years, single molecule techniques have been used to uncover fascinating and unexpected phenomena in polymer physics, including the importance of molecular individualism, dynamic heterogeneity, and molecular subpopulations that underlie the dynamic behavior of materials. In this talk, I will discuss our group’s recent work in extending the field of single polymer dynamics to architecturally complex polymers such as rings, in addition to entangled solutions of linear chains in flow. Ring polymers are a unique class of macromolecules that lack free ends and show qualitatively different dynamics compared to linear polymers. In dilute solution, ring polymers undergo a coil-stretch transition in extensional flow that is different than linear polymers due to a coupling between chain architecture and hydrodynamic interactions (HI), resulting in an ‘open loop’ conformation in flow. We further study the dynamics of rings in shear flow using a custom flow-gradient shear device for fluorescence microscopy. In shear flow, single rings undergo end-over-end tumbling events and tank-treading-like motion that is markedly different than linear chains. Upon increasing polymer concentration, we also study the dynamics of rings in semi-dilute solutions of pure linear chains or blends of ring-linear chains. Surprisingly, the relaxation dynamics of rings in semi-dilute unentangled solutions reveals the emergence of multiple molecular sub-populations, which is analogous to the relaxation of linear chains in the entangled regime. Finally, we study the nonequilibrium stretching dynamics of rings in semi-dilute blends of ring-linear polymers in extensional flow, which reveals unexpected fluctuations in chain extension, even at ‘steady-state’. Brownian dynamics simulations are used to complement single molecule experiments, which show that ring extension fluctuations arise due to a combination of intermolecular HI effects and threading of linear polymers through rings. Overall, our work shows that molecular behavior is markedly heterogeneous in non-dilute polymer solutions, which showcases the power of single molecule techniques to understand the nonequilibrium dynamics of soft materials.