Paper Number
PO22
Session
Poster Session
Title
Intermolecular hooking in unentangled semidilute polymer solutions under extensional flow
Presentation Date and Time
October 23, 2019 (Wednesday) 6:30
Track / Room
Poster Session / Ballroom C on 4th floor
Authors
- Young, Charles D. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
- Sing, Charles E. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Charles D. Young and Charles E. Sing
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Young, Charles D.
Text of Abstract
Polymer solution dynamics and rheology are relevant to a wide range of processing methods. Developing an understanding of the polymer conformational dynamics and the emergent material properties is challenging because of the interplay of hydrodynamic interactions (HI), excluded volume (EV), and topological constraints driven by concentration and polymer architecture. This is particularly true when extensional flow is introduced, which strongly deforms the polymers from their equilibrium conformations. Using a new technique for rapid Brownian dynamics (BD) simulation, which we call the iterative conformational averaging (CA) method, we investigate the dynamics and rheology of linear, comb, and ring polymer solutions at concentrations increasing from the dilute limit to the entanglement crossover point. We apply a step strain rate planar extensional flow to the equilibrium solution and quantify the dynamics in startup, at steady state, and after flow cessation via conformational distributions and the polymer contribution to extensional viscosity. We show that flow enhances intermolecular HI and topological interactions, resulting in transient intermolecular entanglements and concentration dependent rheology below the overlap concentration c*. Interestingly, each polymer architecture exhibits unique molecular conformations. We characterize this molecular individualism as a function of polymer concentration, strain rate, and molecular weight. We establish connections between entangled populations and the ensemble average conformational distributions and solution stress. We also compare to scaling theories, which predict the coexistence of coiled and stretched conformations on the basis of conformation dependent HI.