From Wall Slip to Bulk Shear Banding in Entangled Polymer Solutions

Wang, Shi‐Qing

doi:10.1002/macp.201800327

Cited by 10 publications

(6 citation statements)

References 100 publications

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“…Hence, we hypothesize that the low-viscosity puddles, which are present exclusively in the high SRB, originate microscopically from shear-induced chain stretching and alignment. This hypothesis is consistent with molecular dynamics simulations, ,− where the shear banding of entangled polymer fluids is associated with shear-induced local disentanglement of polymer networks in the high-SRB …”

Section: Discussionsupporting

confidence: 88%

“…Such spatially distinct dumbbell dynamics shed new light onto the microscopic origin of shear banding in concentrated polymer solutions and provide important insights into the dynamics of polymer chains in shear-banding flows. We conclude by discussing the implication of our experimental findings for existing shear-banding theories. − ,,,,− …”

Section: Introductionmentioning

confidence: 66%

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Dynamics of DNA-Bridged Dumbbells in Concentrated, Shear-Banding Polymer Solutions

et al. 2021

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Although experimental evidence for shear-banding flows in concentrated polymer solutions has accumulated over the last 20 years, the origin of such shear-banding flows is still under heated debate. Experiments that probe the microscopic dynamics of shear-banding polymer solutions are still scarce. Here, using a custom-built high-resolution rheo-confocal shear cell, we experimentally study the dynamics of DNA-bridged colloidal dumbbells in the shear-banding flow of concentrated double-stranded DNA (dsDNA) solutions under large amplitude oscillatory shear. We synthesize dumbbells consisting of two spherical colloids linked by λ-DNA and track their 2D-projected configurations in sheared dsDNA solutions. We first confirm that the velocity profile of the concentrated dsDNA solutions is inhomogeneous at high Weissenberg numbers and exhibits strong shear banding with two distinct shear bands. We then measure the orientational distribution of the DNA-bridged dumbbells and investigate their translational and rotational dynamics within the two shear bands. The preferred alignment of the dumbbells along the flow direction in the high-shear-rate band suggests the dominant role of elastic stresses in that band. In contrast, a bimodal distribution of dumbbell orientations is observed in the low-shear-rate band, indicating more balanced contributions from both normal and elastic stresses. Furthermore, exclusively in the high-shear-rate band, we also find spatially localized correlated enhanced translational and rotational motions and a strong coupling between enhanced translation and chain extension. These unique conformational and dynamic features suggest shear-induced breakage of the local entanglement network in the high-shear band, which we postulate leads to puddles of low viscosity within an otherwise high-viscosity fluid. Together, our quantitative analyses of the spatially distinct dynamics of dsDNA-bridged dumbbells in coexisting shear bands provide important insights into the microscopic origin of shear-banding flows in concentrated polymer solutions.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 66%

Dynamics of DNA-Bridged Dumbbells in Concentrated, Shear-Banding Polymer Solutions

et al. 2021

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“…However, this no-slip boundary condition will not be valid for many complex fluids, such as polymer solutions. Especially at higher polymer concentrations things become even more complicated when a thin polymer-depleted layer of much lower viscosity than the bulk solution forms at the solid boundary, in which the surface wettability plays a crucial role [73][74][75][76][77]. One of the open questions in centrifugal spinning that has not been dealt with in detail, to our knowledge, is the effect of nozzle material on the final fiber morphology.…”

Section: Polymer Solution-wall Interactionsmentioning

confidence: 99%

Influence of Polymer Concentration and Nozzle Material on Centrifugal Fiber Spinning

et al. 2020

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Centrifugal fiber spinning has recently emerged as a highly promising alternative technique for the production of nonwoven, ultrafine fiber mats. Due to its high production rate, it could provide a more technologically relevant fiber spinning technique than electrospinning. In this contribution, we examine the influence of polymer concentration and nozzle material on the centrifugal spinning process and the fiber morphology. We find that increasing the polymer concentration transforms the process from a beaded-fiber regime to a continuous-fiber regime. Furthermore, we find that not only fiber diameter is strongly concentration-dependent, but also the nozzle material plays a significant role, especially in the continuous-fiber regime. This was evaluated by the use of a polytetrafluoroethylene (PTFE) and an aluminum nozzle. We discuss the influence of polymer concentration on fiber morphology and show that the choice of nozzle material has a significant influence on the fiber diameter.

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“…The shear-induced instability in such complex fluids and simple viscoelastic liquids can be understood in a unified manner by using the mapping of c ↔  and  ↔ p (31), where c is the concentration and  is the osmotic pressure in the complex fluids. However, rather a few studies have been conducted on the shear-induced instability of complex fluids influenced by a boundary wall (59)(60)(61)(62)(63)(64)(65)(66)(67). In this case, the liquid-rich dilute phase is to be formed near the walls for such a mixture to reduce viscous dissipation, as the gas phase is formed for a simple liquid.…”

Section: Discussionmentioning

confidence: 99%

A novel physical mechanism of liquid flow slippage on a solid surface

Kurotani

Tanaka

2020

Sci. Adv.

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Viscous liquids often exhibit flow slippage on solid walls. The occurrence of flow slippage has a large impact on the liquid transport and the resulting energy dissipation, which are crucial for many applications. It is natural to expect that slippage takes place to reduce the dissipation. However, (i) how the density fluctuation is affected by the presence of the wall and (ii) how slippage takes place through forming a gas layer remained elusive. Here, we report possible answers to these fundamental questions: (i) Density fluctuation is intrinsically enhanced near the wall even in a quiescent state irrespective of the property of wall, and (ii) it is the density dependence of the viscosity that destabilizes the system toward gas-layer formation under shear flow. Our scenario of shear-induced gas-phase formation provides a natural physical explanation for wall slippage of liquid flow, covering the slip length ranging from a microscopic (nanometers) to macroscopic (micrometers) scale.

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From Wall Slip to Bulk Shear Banding in Entangled Polymer Solutions

Cited by 10 publications

References 100 publications

Dynamics of DNA-Bridged Dumbbells in Concentrated, Shear-Banding Polymer Solutions

Dynamics of DNA-Bridged Dumbbells in Concentrated, Shear-Banding Polymer Solutions

Influence of Polymer Concentration and Nozzle Material on Centrifugal Fiber Spinning

A novel physical mechanism of liquid flow slippage on a solid surface

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