We use nonequilibrium atomistic molecular dynamics simulations of unentangled melts of linear and star oligomer chains ( ) to study the steady-state viscoelastic response under confinement within nanoscale hematite channels. We report (i) the negative (positive) first (second) normal stress difference and (ii) the presence of viscoelastic tension at low . With the aim of uncovering the molecular mechanism of viscoelasticity, we link these effects to bond alignment such that absorbed chains near the surface can carry the elastic force exerted on the walls, which decays as the chains become more aligned in the flow direction. This alignment is observed to be independent of the film thickness but enhanced as the shear rate increases or the surface attraction weakens.
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May 2024
Research Article|
March 21 2024
Molecular rheology of nanoconfined oligomer melts
A. B. Yıldırım
;
A. B. Yıldırım
1
Department of Mechanical Engineering, Bilkent University
, Ankara, Turkey
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A. Erbaş
;
A. Erbaş
2
UNAM—National Nanotechnology Research Center and Institute of Materials Science and Nanotechnology, Bilkent University
, Ankara, Turkey
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L. Biancofiore
L. Biancofiore
a)
1
Department of Mechanical Engineering, Bilkent University
, Ankara, Turkey
2
UNAM—National Nanotechnology Research Center and Institute of Materials Science and Nanotechnology, Bilkent University
, Ankara, Turkey
3
Department of Industrial Engineering, Information and Economics, University of L’Aquila, Piazzale Ernesto Pontieri, Monteluco di Roio
, L’Aquila, Italy
a)Author to whom correspondence should be addressed; electronic mail: luca.biancofiore@univaq.it
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a)Author to whom correspondence should be addressed; electronic mail: luca.biancofiore@univaq.it
J. Rheol. 68, 285–299 (2024)
Article history
Received:
August 25 2023
Accepted:
February 17 2024
Citation
A. B. Yıldırım, A. Erbaş, L. Biancofiore; Molecular rheology of nanoconfined oligomer melts. J. Rheol. 1 May 2024; 68 (3): 285–299. https://doi.org/10.1122/8.0000751
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