Vorticity banding during the lamellar-to-onion transition in a lyotropic surfactant solution in shear flow

Wilkins, Georgina M. H.; Olmsted, Peter D.

doi:10.1140/epje/i2006-10053-9

Cited by 33 publications

(34 citation statements)

References 56 publications

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“…Gradient shear banding, that is the occurence of bands with different shear rates, stacked along the velocity gradient, is a likely scenario during the inhomogeneous MLV-to-layer transition [16] since MLVs and aligned lamellae have different viscosities. There has also been a report on the observation of vorticity shear banding, i.e., of bands of different stress stacked along the vorticity axis, during the lamellar-to-onion transition [61] but we have seen no evidence B. Medronho et al of this in our NMR studies.…”

Section: Introductioncontrasting

confidence: 59%

Transient and Steady-State Shear Banding in a Lamellar Phase as Studied by Rheo-NMR

Medronho

Olsson

Schmidt

et al. 2012

Zeitschrift Für Physikalische Chemie

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Flow fields and shear-induced structures in the lamellar (L α ) phase of the system triethylene glycol mono n-decyl ether (C 10 E 3 )/water were investigated by NMR velocimetry, diffusometry, and 2 H NMR spectroscopy. The transformation from multilamellar vesicles (MLVs) to aligned planar lamellae is accompanied by a transient gradient shear banding. A high-shear-rate band of aligned lamellae forms next to the moving inner wall of the cylindrical Couette shear cell while a low-shear-rate band of the initial MLV structure remains close to the outer stationary wall. The band of layers grows at the expense of the band of MLVs until the transformation is completed. This process scales with the applied strain. Wall slip is a characteristic of the MLV state, while aligned layers show no deviation from Newtonian flow. The homogeneous nature of the opposite transformation from well aligned layers to MLVs via an intermediate structure resembling undulated multilamellar cylinders is confirmed. The strain dependence of this transformation appears to be independent of temperature. The shear diagram, which represents the shear-induced structures as a function of temperature and shear rate, contains a transition region between stable layers and stable MLVs. The steady-state structures in the transition region show a continuous change from layer-like at high temperature to MLV-like at lower temperature. These structures are homogeneous on a length scale above a few micrometers.

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Section: Introductioncontrasting

confidence: 59%

Transient and Steady-State Shear Banding in a Lamellar Phase as Studied by Rheo-NMR

Medronho

Olsson

Schmidt

et al. 2012

Zeitschrift Für Physikalische Chemie

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“…Vorticity banding is some times observed when discontinuous (or very strong) shear thickening occurs (like for the worm-like micelles in Bonn et al 1998, Wilkins and Olmsted 2006, and Fischer et al 2002, where the shear stress exhibits a (quasi-)discontinuity, like in Fig. 10b (but not necessarily followed by shear thinning).…”

Section: Vorticity Bandingmentioning

confidence: 95%

“…The bands that are stacked along the vorticity direction (as sketched in the right Fig. 1) are visible either due to differences in optical birefringence (like for the rodlike colloids in Dhont et al 2003 andKang et al 2006) and the onions in Wilkins and Olmsted (2006) or turbidity (like the worm-like micelles in Fischer et al 2002). In some of these systems (Bonn et al 1998;Chen et al 1992), a van der Waals loop in the stress is found, so that it seems that both gradient and vorticity banding can occur.…”

Section: Vorticity Bandingmentioning

confidence: 99%

“…Vorticity banding has been observed in surfactant systems forming multi-lamellar vesicles (onions; Bonn et al 1998;Wilkins and Olmsted 2006), crystallizing colloids (Chen et al 1992), surfactant solutions (Fischer et al 2002), dispersions of semirigid, rod-like colloids (Dhont et al 2003;Kang et al 2006), and nanotube suspensions where flow-induced, highly elastic clusters are formed (LinGibson et al 2004). It should be mentioned that the solidlike clusters in Lin-Gibson et al (2004) align along the vorticity direction in a log-rolling state.…”

Section: Vorticity Bandingmentioning

confidence: 99%

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Gradient and vorticity banding

2008

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"Banded structures" of macroscopic dimensions can be induced by simple shear flow in many different types of soft matter systems. Depending on whether these bands extend along the gradient or vorticity direction, the banding transition is referred to as "gradient banding" or "vorticity banding," respectively. The main features of gradient banding can be understood on the basis of a relatively simple constitutive equation. This minimal model for gradient banding will be discussed in some detail, and its predictions are shown to explain many of the experimentally observed features. The minimal model assumes a decrease of the shear stress of the homogeneously sheared system with increasing shear rate within a certain shear-rate interval. The possible microscopic origin of the severe shear-thinning behaviour that is necessary for the resulting nonmonotonic flow curves is discussed for a few particular systems. Deviations between experimental observations and predictions by the minimal model are due to obvious simplifications within the scope of the minimal model. The most serious simplifications are the neglect of concentration dependence of the shear stress (or on other degrees of freedom) and of the elastic contributions to the stress, normal stresses, and the possibility of shear-induced phase transitions. The consequences of coupling of stress and concentration will be analyzed in some detail. In contrast to predictions of the minimal model, when coupling to concentration is important, a flow instability can occur that does not require strong shear thinning. Gradient banding is sometimes also observed in glassy-and gel-like systems, as well as in shear-thickening systems. Possible mechanisms that could be at the origin of gradient-band formation in such systems are discussed. Gradient banding can also occur in strongly entangled polymeric systems. Banding in these systems is discussed on the basis of computer simulations. Vorticity banding is less well understood and less extensively investigated experimentally as compared to gradient banding. Possible scenarios that are at the origin of vorticity banding will be discussed. Among other systems, the observed vorticity-banding transition in rod-like col-loids is discussed in some detail. It is argued, on the basis of experimental observations for these colloidal systems, that the vorticity-banding instability for such colloidal suspensions is probably related to an elastic instability, reminiscent of the Weissenberg effect in polymeric systems. This mechanism might explain vorticity banding in discon-tinuously shear-thickening systems and could be at work in other vorticity-banding systems as well. This overview does not include time-dependent phenomena like oscillations and chaotic behaviour.

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“…Flow-induced pattern formation leading to banded regions is a quite general phenomenon in complex fluids, being found in wormlike micellar solutions [1], rodlike virus suspensions [2], attractive emulsions [3], lyotropic liquid crystals [4], suspensions of rigid spherical particles [5], supramolecular polymer solutions [6], and granular materials [7]. Band formation in complex fluids has been mostly studied in shear flow, which is shown schematically in Fig.…”

mentioning

confidence: 99%

Shear Banding in Biphasic Liquid-Liquid Systems

2008

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In this Letter, we present the first systematic report of shear-induced banding in microconfined biphasic liquid-liquid systems, i.e., formation of alternating regions of high and low volume fraction of dispersed-phase droplets in a parallel plate flow cell. Such a flow-driven, gap-dependent phenomenon is only observed at low values of the viscosity ratio between the dispersed and the continuous phase, and in a given range of the applied shear rate. Based on rheological measurements, band formation is found to be associated with a viscosity decrease as compared to the homogeneous, structureless case, thus showing that system microstructure is somehow evolving towards reduced viscous dissipation under shear flow.

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Vorticity banding during the lamellar-to-onion transition in a lyotropic surfactant solution in shear flow

Cited by 33 publications

References 56 publications

Transient and Steady-State Shear Banding in a Lamellar Phase as Studied by Rheo-NMR

Transient and Steady-State Shear Banding in a Lamellar Phase as Studied by Rheo-NMR

Gradient and vorticity banding

Shear Banding in Biphasic Liquid-Liquid Systems

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