Stress Relaxation in Highly Oriented Melts of Entangled Polymers

doi:10.1021/acs.macromol.9b01161

This content will become publicly available on October 21, 2020

Title: Stress Relaxation in Highly Oriented Melts of Entangled Polymers

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Abstract

Here, molecular dynamics simulations are used to study relaxation of entangled polymer melts deformed far from equilibrium by uniaxial extensional flow. Melts are elongated to a Hencky strain of 6 at Rouse–Weissenberg numbers from 0.16 to 25, producing states with a wide range of chain alignment. Then flow is ceased and the systems are allowed to relax until twice the equilibrium disentanglement time. The relaxation of the stress is correlated with changes in the conformation of chains and the geometry of the tube confining them. Independent of initial alignment, chains relax to conformations consistent with the equilibrium tube length and diameter on the equilibrium Rouse time. Subsequent relaxation is the same for all systems and controlled by the equilibrium distentanglement time. These results are counter to prior work that indicates orientation causes a large, stretch-dependent reduction in the entanglement density that can only be recovered slowly by reptation on the equilibrium disentanglement time, raising fundamental questions about the nature of entanglement in aligned polymer melts.

Authors:

^[1]; Hopkins, Austin ^[2];

^[2]

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Johns Hopkins Univ., Baltimore, MD (United States)

Publication Date:: 2019-10-21

Research Org.:: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:: USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)

OSTI Identifier:: 1574479

Report Number(s):: SAND-2019-13792J
Journal ID: ISSN 0024-9297; 681376

Grant/Contract Number:: AC04-94AL85000; NA-0003525

Resource Type:: Accepted Manuscript

Journal Name:: Macromolecules

Additional Journal Information:: Journal Name: Macromolecules; Journal ID: ISSN 0024-9297

Publisher:: American Chemical Society

Country of Publication:: United States

Language:: English

Citation Formats


                    O’Connor, Thomas C., Hopkins, Austin, and Robbins, Mark O. Stress Relaxation in Highly Oriented Melts of Entangled Polymers.  United States: N. p., 2019. 
        Web.  doi:10.1021/acs.macromol.9b01161.

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                    O’Connor, Thomas C., Hopkins, Austin, & Robbins, Mark O. Stress Relaxation in Highly Oriented Melts of Entangled Polymers.  United States.  doi:10.1021/acs.macromol.9b01161.

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                    O’Connor, Thomas C., Hopkins, Austin, and Robbins, Mark O. Mon .  
        "Stress Relaxation in Highly Oriented Melts of Entangled Polymers".  United States.  doi:10.1021/acs.macromol.9b01161.

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@article{osti_1574479,

  title        = {Stress Relaxation in Highly Oriented Melts of Entangled Polymers},

  author       = {O’Connor, Thomas C. and Hopkins, Austin and Robbins, Mark O.},

  abstractNote = {Here, molecular dynamics simulations are used to study relaxation of entangled polymer melts deformed far from equilibrium by uniaxial extensional flow. Melts are elongated to a Hencky strain of 6 at Rouse–Weissenberg numbers from 0.16 to 25, producing states with a wide range of chain alignment. Then flow is ceased and the systems are allowed to relax until twice the equilibrium disentanglement time. The relaxation of the stress is correlated with changes in the conformation of chains and the geometry of the tube confining them. Independent of initial alignment, chains relax to conformations consistent with the equilibrium tube length and diameter on the equilibrium Rouse time. Subsequent relaxation is the same for all systems and controlled by the equilibrium distentanglement time. These results are counter to prior work that indicates orientation causes a large, stretch-dependent reduction in the entanglement density that can only be recovered slowly by reptation on the equilibrium disentanglement time, raising fundamental questions about the nature of entanglement in aligned polymer melts.},

  doi          = {10.1021/acs.macromol.9b01161},

  journal      = {Macromolecules},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {2019},

  month        = {10}

}

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DOI: 10.1021/acs.macromol.9b01161

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