Paper Number
PS23 

Session
Polymers in Solution

Title
Direct observation of ring polymer dynamics in semi-dilute solutions: Coupling of molecular topology and interchain interactions

Presentation Date and Time
October 16, 2018 (Tuesday) 3:45

Track / Room
Track 4 / Post Oak

Authors (Click on name to view author profile)

1. Zhou, Yuecheng (University of Illinois at Urbana-Champaign, Materials Science and Engineering)
2. Regan, Kathryn (University of San Diego)
3. Kong, Dejie (Texas Tech University, Department of Chemical Engineering)
4. Banik, Sourya (Texas Tech University, Department of Chemical Engineering)
5. Robertson-Anderson, Rae M. (University of San Diego, Department of Physics and Biophysics)
6. McKenna, Gregory B. (Texas Tech University, Department of Chemical Engineering)
7. Schroeder, Charles M. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Yuecheng Zhou¹, Kathryn Regan², Dejie Kong³, Sourya Banik³, Rae M. Robertson-Anderson², Gregory B. McKenna³, and Charles M. Schroeder^4
1Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; ²Department of Physics and Biophysics, University of San Diego, San Diego, CA 92110; ³Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409; ⁴Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Zhou, Yuecheng

Text of Abstract
Over the past two decades, advances in fluorescence imaging have enabled the direct observation of polymer dynamics at the single molecule level. Despite recent progress, the vast majority of studies has mainly focused on the dynamics of linear polymer chains in dilute solutions. Moving forward, there is a clear need to study the dynamics of polymers with complex molecular topologies such as ring polymers in flow. Here, we report the direct observation of ring polymer dynamics in semi-dilute unentangled solutions of linear chains in extensional flow. In particular, we characterize the transient and steady-state stretching dynamics of ring polymers in background solutions of semi-dilute linear chains across a wide range of concentrations. Remarkably, our results show that ring polymers drastically fluctuate in chain extension in extensional flow, even at so-called 'steady-state', long after the initial transient stretching process. Interestingly, such large extensional fluctuations are not observed in the steady-state stretching of linear polymers in semi-dilute solutions in extensional flows. Furthermore, even at very low concentrations of linear chains (0.025 c*), we see large fluctuations of ring molecules in the linear background that are different from the linear chains. Based on these results, we hypothesize that ring polymer fluctuations arise due to transient threading of linear polymers through open ring polymer chains in flow. The fluctuation frequency is analyzed as a function of strain rate and background polymer concentration. Moreover, our results show that ring polymers generally exhibit markedly less molecular individualism across the molecular ensemble compared to their linear counterparts during transient stretching in extensional flow, which is attributed to circular topological constraints. Overall, this work effectively extends the study of single polymer dynamics to ring-shaped polymers in non-dilute solutions.