Microscopic theory of convective constraint release

Milner, Scott T.; McLeish, Tom; Likhtman, Alexei E.

doi:10.1122/1.1349122

Cited by 148 publications

(172 citation statements)

References 21 publications

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“…Note that tubemodel theories can account for the fast flow-induced disentanglement leading to shear thinning (the so-called convected constraint release) 23 and associated shear banding. 24 In fact, a rather refined analysis of the shear-rate dependence of the release of entanglement constraints is now available based on these ideas, 25,26 although this issue is currently much under debate.…”

Section: Introductionmentioning

confidence: 99%

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

Briels¹,

Vlassopoulos²,

Kang³

et al. 2011

The Journal of Chemical Physics

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A semimicroscopic derivation is presented of equations of motion for the density and the flow velocity of concentrated systems of entangled polymers. The essential ingredient is the transient force that results from perturbations of overlapping polymers due to flow. A Smoluchowski equation is derived that includes these transient forces. From this, an equation of motion for the polymer number density is obtained, in which body forces couple the evolution of the polymer density to the local velocity field. Using a semimicroscopic Ansatz for the dynamics of the number of entanglements between overlapping polymers, and for the perturbations of the pair-correlation function due to flow, body forces are calculated for nonuniform systems where the density as well as the shear rate varies with position. Explicit expressions are derived for the shear viscosity and normal forces, as well as for nonlocal contributions to the body force, such as the shear-curvature viscosity. A contribution to the equation of motion for the density is found that describes mass transport due to spatial variation of the shear rate. The two coupled equations of motion for the density and flow velocity predict flow instabilities that will be discussed in more detail in a forthcoming publication.

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Section: Introductionmentioning

confidence: 99%

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

Briels¹,

Vlassopoulos²,

Kang³

et al. 2011

The Journal of Chemical Physics

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“…property correlation studies have established that the presence of long-chain branching in polymers has a significant impact on the properties of such materials in the melt [1]. However, in the overwhelming majority of cases, industrially produced materials have a wide distribution of chain lengths between branch points, making modelling of the material challenging.…”

mentioning

confidence: 99%

HyperMacs – long chain hyperbranched polymers: A dramatically improved synthesis and qualitative rheological analysis

Clarke

Luca

Dodds

et al. 2008

European Polymer Journal

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. (2008) 'HyperMacs long chain hyperbranched polymers : a dramatically improved synthesis and qualitative rheological analysis.', European polymer journal., 44 (3). pp. 665-676. Further information on publisher's website:http://dx.doi.org/10. 1016/j.eurpolymj.2007.12.022 Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in European Polymer Journal. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in European Polymer Journal, 44, 3, March 2008, 10.1016/j.eurpolymj.2007 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract.We have previously reported a novel (albeit modestly successful) strategy for the synthesis of polystyrene HyperMacs -long chain branched analogues of hyperbranched polymers.The building blocks for HyperMacs, AB 2 macromonomers are synthesized by living anionic polymerization and as such are well-defined in terms of molecular weight and polydispersity but the nature of the coupling reaction used to generate the highly branched HyperMacs results in branched polymers with a distribution of molecular weights and architectures. In our previously reported studies the extent of the coupling reaction was significantly hampered by side reactions, however, we report here dramatic improvements to the coupling chemistry which overcome the previously experienced limitations resulting in a four fold increase in the extent of the coupling reactions.Furthermore we report the effect of the addition of varying amounts of a B 3 core molecule to the coupling reaction and the resultant 'control' of the final molecular weight of the HyperMac. Melt rheology showed polystyrene HyperMacs to be thermorheologically simple, obeying WilliamLandel-Ferry (WLF) behaviour. HyperMacs showed little evidence for relaxation by reptation and when the molecular weight of the macromonomer was ≤ M e for polystyrene, HyperMacs resemble unentangled polymers below the gel point, despite being well above the entanglement molecular weight for linear polystyrene. Increasing the molecular weight of the macromonomer to substantially above Me seems to introduce some entangled nature to the HyperMac as evidenced by the emergence of a near horizontal plateau in G'' -the loss modulus.

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“…11 The subsequent three decades witnessed extensive efforts to improve the original de Gennes-Doi-Edwards model. [12][13][14][15][16][17][18][19][20] Experiments, too many to cite them here, seem to support the theoretical description. 1 However, it is actually not obvious that interchain interactions can be treated in such a smoothed-out manner.…”

Section: Molecular Approach Of Tube Model and Continuum-mechanical Comentioning

confidence: 78%

Nonlinear Polymer Rheology

Wang¹

2017

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Microscopic theory of convective constraint release

Cited by 148 publications

References 21 publications

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

Constitutive equations for the flow behavior of entangled polymeric systems: Application to star polymers

HyperMacs – long chain hyperbranched polymers: A dramatically improved synthesis and qualitative rheological analysis

Nonlinear Polymer Rheology

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