Extensional stress growth and stress relaxation in entangled polymer solutions

Bhattacharjee, Pradipto K.; Nguyễn, Duy Anh; McKinley, Gareth H.; Sridhar, T.

doi:10.1122/1.1530625

Cited by 86 publications

(101 citation statements)

References 28 publications

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“…However, the main concept, the friction reduction due to stretch/orientation (that leads to lack of thickening for melts), sounds reasonable and is, indeed, consistent with recent molecular dynamics (MD) simulations 23,24) and experiments. 4,21,25) 8,9) that has been reported to reproduce the solution data. 7) We incorporated the friction reduction in this toy model 7,9) to examine if the model can consistently describe the behavior of melts and solutions.…”

Section: Introductionmentioning

confidence: 48%

“…Recent experiments have established the thinning feature of the uniaxial steady state elongational viscosity η E for entangled monodisperse linear polystyrene (PS) melts 1,2) and the thickening feature for equally entangled PS solutions, 3,4) both occurring in the same range of strain rate ε 4 higher than the equilibrium Rouse relaxation frequency, w R . The classical Doi-Edwards tube theory 5) (DE theory) assuming a constant chain length cannot describe the thickening of the solutions, whereas the extended tube theory of Marrucci and Grizzuti 6) considering the chain stretch does not reproduce the monotonic thinning for the melts.…”

Section: Introductionmentioning

confidence: 99%

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Concept of Stretch/Orientation-Induced Friction Reduction Tested with a Simple Molecular Constitutive Equation

Yaoita

Masubuchi

Watanabe

2014

J. Soc. Rheol., Jpn

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Under elongational flow at strain rates higher than the Rouse relaxation frequency, entangled polymer melts exhibit thinning of their elongational viscosity whereas equally entangled solutions show thickening. Yaoita et al. [Yaoita et al., Macromolecules 2012, 45, 2773 related this difference between the melts and solutions to reduction of segmental friction on enhancement of the stretch/orientation averaged for the components therein (that includes the solvent for the case of solutions). They analyzed the stress relaxation data after cessation of elongational flow to propose an empirical equation describing this friction reduction as a function of the stretch/orientation factor. Multi-chain slip-link (PCN) simulations considering this friction reduction described the thinning of melts and the thickening of solutions consistently and semi-quantitatively. This study further tests the molecular concept of the stretch/orientation-induced friction reduction with the aid of a simple molecular constitutive equation, a toy version of the Mead-Larson-Doi model [Mead et al., Macromolecules 1998, 31, 7895] (MLD toy model) being modified to incorporate this empirical equation of the friction reduction. The modified toy model mimicked the behavior of melts and solutions consistently. This consistency vanished when the friction reduction in the model was artificially switched off, even though the finite extensible nonlinear elasticity was still taken into account. These results lend further support to the molecular concept of the stretch/orientation-induced friction reduction.

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Section: Introductionmentioning

confidence: 48%

Section: Introductionmentioning

confidence: 99%

Concept of Stretch/Orientation-Induced Friction Reduction Tested with a Simple Molecular Constitutive Equation

Yaoita

Masubuchi

Watanabe

2014

J. Soc. Rheol., Jpn

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“…[1][2][3][4][5][6][7][8][9][10][11] Of particular interest is the lack of strain-hardening observed for entangled polymer melts under fast steady elongational flow, [1][2][3][4][5] which makes a contrast to the significant hardening seen for entangled polymer solutions. [4][5][6][7][8] The hardening of the entangled solutions reflects the finite extensibility of the stress-sustaining subchains (entanglement strands) that allows the highly stretched subchain to become non-Gaussian and behave as a stiffened spring. [5][6][7][8] The lack of hardening for the entangled polymer melts is in turn attributable to a decrease of the segmental friction on the subchain orientation/ stretch that tends to reduce the orientation/stretch and suppress the hardening due to stiffening of the stretched subchain.…”

Section: Introductionmentioning

confidence: 99%

“…This FENE dumbbell model has been fully analyzed mathematically 12) and is now well established as the basic model for highly stretched chain. In fact, the strain-hardening of η E measured for the entangled solutions [4][5][6][7][8] …”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8] The hardening of the entangled solutions reflects the finite extensibility of the stress-sustaining subchains (entanglement strands) that allows the highly stretched subchain to become non-Gaussian and behave as a stiffened spring. [5][6][7][8] The lack of hardening for the entangled polymer melts is in turn attributable to a decrease of the segmental friction on the subchain orientation/ stretch that tends to reduce the orientation/stretch and suppress the hardening due to stiffening of the stretched subchain. [9][10][11] Regarding the above features of entangled polymer melts and solutions, we note that the essence of strain-hardening is related to the stiffening of the stretched chain irrespective of the entanglement.…”

Section: Introductionmentioning

confidence: 99%

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Revisit the Elongational Viscosity of FENE Dumbbell Model

Watanabe

2017

J. Soc. Rheol., Jpn

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It is well known that the elongational viscosity η E of the Hookean dumbbell model increases with increasing elongational strain rate ε and finally diverges to infinite on approach of ε to 1/2τ H eq , where τ H eq is the viscoelastic relaxation time of the Hookean dumbbell that does not change with ε. This divergence of η E reflects infinite extensibility of the Hookean dumbbell. Real polymer chains obviously have the maximum stretch limit, so that the dumbbell model with a finite extensibility was developed almost a half century ago as a model for those chains under strong flow. This model exhibits the finite extensible nonlinear elasticity (FENE) effect under strong flow to provide η E with the strain-hardening feature but without any divergence. This FENE dumbbell model has been mathematically analyzed in detail and is now well established. Nevertheless, in a naive expectation, stiffening of the FENE dumbbell could/should largely increase the viscosity. Thus, it is still desired to explain, on an intuitive physical basis, how the stiffening suppresses the divergence of η E . From this point of view, this study focuses on the effective relaxation time τ eff allows the FENE dumbbell to change its conformation just slightly even for a large increase of ε from 1/2τ H eq to any higher value, which naturally leads to the lack of divergence of η E .

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Rheology of Unentangled Polymer Solutions Depends on Three Macromolecular Properties: Flexibility, Extensibility, and Segmental Dissymmetry

Dinic

Narváez

Sharma

2022

Macromolecular Engineering

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We elucidate the influence of chemical structure on macromolecular hydrodynamics and rheological response using poly(ethylene oxide) or PEO and 2‐hydroxyethyl cellulose (HEC). We contrast the shear rheology response measured using torsional rheometry and find the wellknown universalities like comparable shear viscosity for dilute solutions at comparable degree of chain overlap. We show that dripping‐onto‐substrate (DoS) rheometry protocols that we developed facilitate characterization of pinching dynamics and extensional rheology response even for weakly elastic, low viscosity fluids. Even for unentangled solutions with comparable shear viscosity and molecular weights, the PEO solutions exhibit distinctively higher values of extensional relaxation time, extent of strain hardening, transient extensional viscosity, and an overall delay in pinch‐off. We find that the extensional relaxation times exhibit concentration dependence distinct from shear rheology response, or anticipated by blob models, developed for relaxation of weakly perturbed chains. Most significantly, we show that the influence of polymer choice can be evaluated a priori , using three macromolecular parameters: flexibility, extensibility, and segmental dissymmetry, defined as the ratio of Kuhn length to packing length. We identify the minimum concentration above which elastocapillary response appears and define a stretched overlap concentration below which the extensional relaxation time is concentration independent.

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Extensional stress growth and stress relaxation in entangled polymer solutions

Cited by 86 publications

References 28 publications

Concept of Stretch/Orientation-Induced Friction Reduction Tested with a Simple Molecular Constitutive Equation

Concept of Stretch/Orientation-Induced Friction Reduction Tested with a Simple Molecular Constitutive Equation

Revisit the Elongational Viscosity of FENE Dumbbell Model

Rheology of Unentangled Polymer Solutions Depends on Three Macromolecular Properties: Flexibility, Extensibility, and Segmental Dissymmetry

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