APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019;
Boston, Massachusetts
Session C51: Recent Developments in Nonequilibrium Dynamics and Rheology of Entangled Polymer Liquids
2:30 PM–5:30 PM,
Monday, March 4, 2019
BCEC
Room: 253A
Sponsoring
Unit:
DPOLY
Chair: Shiqing Wang, Univ of Akron
Abstract: C51.00003 : Forced-Based Microscopic Theories of the Equilibrium Dynamics and Nonlinear Rheology of Entangled Rod and Chain Polymer Liquids
3:42 PM–4:18 PM
Abstract
Presenter:
Kenneth Schweizer
(University of Illinois at Urbana-Champaign)
Author:
Kenneth Schweizer
(University of Illinois at Urbana-Champaign)
Using ideas from microscopic glass physics, force-based statistical mechanical theories for the transverse tube confinement field of liquids of zero-excluded-volume rods (needles) and chains have been constructed based solely on dynamic uncrossability which is exactly enforced at the two body level. Coils are coarse grained to chains of self-consistently-determined primitive-path steps. Tube localization emerges above a universal critical degree of interpenetration, and the melt tube diameter scales with packing length. Importantly, the confinement field is anharmonic, softening for large transverse displacements, corresponding to a finite maximum entanglement force. The predicted form of the confinement field is in excellent agreement with f-actin solution experiments and chain melt simulations. The tube field softens with orientation, hardens for affinely stretched chains, and is potentially destroyed beyond a critical stress (microscopic yielding). Nonequilibrium theories and simple constitutive equations under continuous startup shear have been constructed. For chain melts, new physical aspects include a dynamic tension blob scaling construction of a grip force that is the microscopic origin of stretching, a force imbalance criterion for termination of affine deformation and onset of retraction, the influence of entanglement length heterogeneity, an emergent form of convective constraint release, and rate-accelerated retraction of strongly stretched chains. For fast deformations we predict novel fractional power law scalings with rate for the stress overshoot and undershoot, steady state total and orientational stress and contour length stretch, a universal master curve in the elastic-viscous crossover regime, and strong connections between the overshoot and steady state. No adjustable parameter numerical predictions are quantitatively compared with multiple experiments and simulations. This work was done in collaboration with Shi-Jie Xie and Daniel Sussman.