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Title: Molecular Dynamics Investigation of the Relaxation Mechanism of Entangled Polymers after a Large Step Deformation

Abstract

The chain retraction hypothesis of the tube model for nonlinear polymer rheology has been challenged by the recent small-angle neutron scattering (SANS) experiment. In this study, we further examine the microscopic relaxation mechanism of entangled polymer melts after a large step uniaxial extension by using large-scale molecular dynamics simulation. We show that the unique structural features associated with the chain retraction mechanism of the tube model are absent in our simulations, in agreement with the previous experimental results. In contrast to SANS experiments, molecular dynamics simulations allow us to accurately and unambiguously determine the evolution of the radius of gyration tensor of a long polymer chain after a large step deformation. Contrary to the prediction of the tube model, our simulations reveal that the radius of gyration in the perpendicular direction to stretching increases monotonically toward its equilibrium value throughout the stress relaxation. These results provide a critical step in improving our understanding of nonlinear rheology of entangled polymers.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
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  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1479793
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
ACS Macro Letters
Additional Journal Information:
Journal Volume: 7; Journal Issue: 2; Journal ID: ISSN 2161-1653
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Xu, Wen -Sheng, Carrillo, Jan-Michael Y., Lam, Christopher N., Sumpter, Bobby G., and Wang, Yangyang. Molecular Dynamics Investigation of the Relaxation Mechanism of Entangled Polymers after a Large Step Deformation. United States: N. p., 2018. Web. doi:10.1021/acsmacrolett.7b00900.
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Xu, Wen -Sheng, Carrillo, Jan-Michael Y., Lam, Christopher N., Sumpter, Bobby G., & Wang, Yangyang. Molecular Dynamics Investigation of the Relaxation Mechanism of Entangled Polymers after a Large Step Deformation. United States. doi:10.1021/acsmacrolett.7b00900.
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Xu, Wen -Sheng, Carrillo, Jan-Michael Y., Lam, Christopher N., Sumpter, Bobby G., and Wang, Yangyang. Thu . "Molecular Dynamics Investigation of the Relaxation Mechanism of Entangled Polymers after a Large Step Deformation". United States. doi:10.1021/acsmacrolett.7b00900. https://www.osti.gov/servlets/purl/1479793.
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@article{osti_1479793,
title = {Molecular Dynamics Investigation of the Relaxation Mechanism of Entangled Polymers after a Large Step Deformation},
author = {Xu, Wen -Sheng and Carrillo, Jan-Michael Y. and Lam, Christopher N. and Sumpter, Bobby G. and Wang, Yangyang},
abstractNote = {The chain retraction hypothesis of the tube model for nonlinear polymer rheology has been challenged by the recent small-angle neutron scattering (SANS) experiment. In this study, we further examine the microscopic relaxation mechanism of entangled polymer melts after a large step uniaxial extension by using large-scale molecular dynamics simulation. We show that the unique structural features associated with the chain retraction mechanism of the tube model are absent in our simulations, in agreement with the previous experimental results. In contrast to SANS experiments, molecular dynamics simulations allow us to accurately and unambiguously determine the evolution of the radius of gyration tensor of a long polymer chain after a large step deformation. Contrary to the prediction of the tube model, our simulations reveal that the radius of gyration in the perpendicular direction to stretching increases monotonically toward its equilibrium value throughout the stress relaxation. These results provide a critical step in improving our understanding of nonlinear rheology of entangled polymers.},
doi = {10.1021/acsmacrolett.7b00900},
journal = {ACS Macro Letters},
number = 2,
volume = 7,
place = {United States},
year = {2018},
month = {1}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI:  10.1021/acsmacrolett.7b00900
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Cited by: 15 works
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Figures / Tables:

Figure 1 Figure 1: Mean-square internal distance 〈R2(𝑠)〉 divided by the chemical distance 𝑠 for various chain lengths. s = |𝑖 ― 𝑗| is the difference in indices of two beads 𝑖 and 𝑗 within a chain. The results for 𝑁 = 40, 120, and 500 are included here as references. Errormore » bars represent the standard deviations over ten independent simulations. The gray solid line is the benchmark function in the literature.41« less
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Works referencing / citing this record:

Recovery rheology via rheo‐SANS: Application to step strains under out‐of‐equilibrium conditions
journal, October 2019

  • Lee, Johnny C. ‐W.; Porcar, Lionel; Rogers, Simon A.
  • AIChE Journal, Vol. 65, Issue 12
  • DOI: 10.1002/aic.16797

Nonlinear shear of entangled polymers from nonequilibrium molecular dynamics
journal, November 2019

  • Anwar, Muhammad; Graham, Richard S.
  • Journal of Polymer Science Part B: Polymer Physics, Vol. 57, Issue 24
  • DOI: 10.1002/polb.24904

Entangled chain polymer liquids under continuous shear deformation: consequences of a microscopically anharmonic confining tube
journal, January 2018

  • Xie, Shi-Jie; Schweizer, Kenneth S.
  • Soft Matter, Vol. 14, Issue 34
  • DOI: 10.1039/c8sm01182f

Dynamical structure of entangled polymers simulated under shear flow
journal, August 2018

  • Korolkovas, Airidas; Gutfreund, Philipp; Wolff, Max
  • The Journal of Chemical Physics, Vol. 149, Issue 7
  • DOI: 10.1063/1.5035170

Simulation of semidilute polymer solutions in planar extensional flow via conformationally averaged Brownian noise
journal, September 2019

  • Young, Charles D.; Sing, Charles E.
  • The Journal of Chemical Physics, Vol. 151, Issue 12
  • DOI: 10.1063/1.5122811

Slip-Spring and Kink Dynamics Models for Fast Extensional Flow of Entangled Polymeric Fluids
journal, March 2019

  • Moghadam, Soroush; Saha Dalal, Indranil; Larson, Ronald
  • Polymers, Vol. 11, Issue 3
  • DOI: 10.3390/polym11030465
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