Nonlinear Polymer Rheology

Wang, Shi‐Qing

doi:10.1002/9781119029038

Cited by 22 publications

(17 citation statements)

References 22 publications

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“…This extension would permit the study of extremely interesting phenomena such as nonlinear relaxation, stress overshoot, yielding, which represent still open challenges for rheology and condensed matter in general. One relevant question which our work poses is the possibility of having holographic models displaying strain thinning [12,66], in contrast to strain hardening. This issue is also related to the understanding of the physical reasons behind the strain hardening phenomenon we observe, such as possible entropic effects [67].…”

Section: Discussionmentioning

confidence: 99%

“…The fundamental difficulties are twofold: (I) it is conceptually hard to incorporate dissipation into the effective field theory description of solid materials [8,9] because of the unavoidable requirement of unitarity; (II) hydrodynamics and the theory of mechanical deformations are at first sight completely different and it is not clear how to build a unified description using a common language. The problem becomes even more acute when the amplitude of the applied external strain is not small and the linear approximation is of no help anymore -the onset of nonlinear viscoelasticity [10][11][12]. See [13] for a complete treatment of viscoelasticity.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear Oscillatory Shear Tests in Viscoelastic Holography

2020

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We provide the first characterization of the nonlinear and time dependent rheologic response of viscoelastic bottom-up holographic models. More precisely, we perform oscillatory shear tests in holographic massive gravity theories with finite elastic response, focusing on the large amplitude oscillatory shear (LAOS) regime. The characterization of these systems is done using several techniques: (I) the Lissajous figures, (II) the Fourier analysis of the stress signal, (III) the Pipkin diagram and (IV) the dependence of the storage and loss moduli on the amplitude of the applied strain. We find substantial evidence for a strong strain hardening mechanism, possibly related with the strong interactions regime of our dual field theory. Additionally, a crossover between a viscoelastic liquid regime at small graviton mass (compared to the temperature scale), and a viscoelastic solid regime at large values is observed. Finally, we discuss the relevance of our results for soft matter and for the understanding of the widely used homogeneous holographic models with broken translations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nonlinear Oscillatory Shear Tests in Viscoelastic Holography

2020

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“…Despite this extension of the tube model in the nonlinear regime, large discrepancies between theory and experimental results still persist today. In particular, experimental data show that polystyrene (PS) melts adopt a monotonous extension thinning behavior with a scaling of η E ∝ M W ε̇ –0.5 , while PS solutions with the same Z initially exhibit extensional thinning and, at elongation rates comparable to the reciprocal Rouse time τ R –1 , switch to an extension-thickening behavior. − These experimental observations contradict the standard molecular theory, which predicts, for all entangled systems, an upturn of the extensional viscosity beyond ε̇ = τ R –1 due to the rapid stretching of the chains . This unexpected difference of the qualitative behavior between polymer melts and solutions potentially suggests that additional mechanisms need to be added to the model to capture the correct molecular picture.…”

Section: Introductionmentioning

confidence: 97%

Investigating the Transition between Polymer Melts and Solutions in Nonlinear Elongational Flow

et al. 2021

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The Doi-Edwards tube model, coupled with relaxation mechanisms such as reptation, contour length fluctuation and constraint release, allows to quantitatively predict the linear viscoelastic properties of entangled polymers. However, for non-linear elongational flows, large discrepancies between theoretical predictions based on the tube model and experimental results still persist today. This is in particular obvious for the experimentally observed strong qualitative differences in extensional flow of entangled polystyrene (PS) melts and solutions, despite having the same number of entanglements and exhibiting the same linear viscoelastic behaviour. The cause of this non-universality is often attributed either to a monomeric friction reduction, or to an interchain pressure effect.In this work, we investigate the changes in extensional flow behavior going from polymer solutions to the melt state. For this purpose, we measure with a filament stretching rheometer the non-linear extensional responses of differently long PS chains, both in the melt state and diluted in short chain matrices of the same polymer at varying concentrations. These concentrations have been chosen sufficiently high, such that the chains stay entangled. This allows us to discuss the influence of concentration and molar mass on the steady state elongational viscosity to highlight scaling relations.The purpose of the present work is to conduct well-defined experiments to further investigate how the steady extensional viscosity of polymer solutions and blends varies with the concentration and with the molecular weight of the chains

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“…Under strong shear, an entangled polymeric fluid can develop heterogeneous flow profiles with multiple bands of different shear rates [1,2]. Such shear-banding behavior has attracted great research interests in recent years.…”

Section: Introductionmentioning

confidence: 99%

Effect of edge disturbance on shear banding in polymeric solutions

Shin

Dorfman

Cheng

2018

Journal of Rheology

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Edge instabilities are believed to be one of the possible causes of shear banding in entangled polymeric fluids. Here, we investigate the effect of edge disturbance on the shear-induced dynamics of well-entangled DNA solutions. Using a custom high-aspect-ratio planar-Couette cell, we systematically measure the velocity profiles of sheared DNA samples at different distances away from the edge of the shear cell. Under a weak oscillatory shear with the corresponding Weissenberg number (Wi) smaller than 1, where DNA solutions exhibit linear velocity profiles with strong wall slip, the penetration depth of the edge disturbance is on the order of the gap thickness of the shear cell, consistent with the behavior of Newtonian fluids. However, under a strong oscillatory shear with Wi > 1 that produces shear-banding flows, the penetration depth is an order of magnitude larger than the gap thickness and becomes spatially anisotropic. Moreover, we find that the shear-banding flows persist deep inside the sheared sample, where the effect of edge disturbance diminishes. Hence, our experiments demonstrate an abnormally long penetration depth of edge disturbance and illustrate the bulk nature of shear-banding flows of entangled polymeric fluids under time-dependent oscillatory shear.

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Nonlinear Polymer Rheology

Cited by 22 publications

References 22 publications

Nonlinear Oscillatory Shear Tests in Viscoelastic Holography

Nonlinear Oscillatory Shear Tests in Viscoelastic Holography

Investigating the Transition between Polymer Melts and Solutions in Nonlinear Elongational Flow

Effect of edge disturbance on shear banding in polymeric solutions

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