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Walter Richtering - One of the best experts on this subject based on the ideXlab platform.
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shear induced morphology transition and microPhase separation in a Lamellar Phase doped with clay particles
Langmuir, 2004Co-Authors: Florian Nettesheim, Peter Lindner, Isabelle Grillo, Walter RichteringAbstract:We report on the influence of shear on a nonionic Lamellar Phase of tetraethyleneglycol monododecyl ether (C 1 2 E 4 ) in D 2 O containing clay particles (Laponite RD). The system was studied by means of small-angle light scattering (SALS) and small-angle neutron scattering (SANS) under shear. The SANS experiments were conducted using a H 2 O/D 2 O mixture of the respective scattering length density to selectively match the clay scattering. The rheological properties show the familiar shear thickening regime associated with the formation of multiLamellar vesicles (MLVs) and a shear thinning regime at higher stresses. The variation of viscosity is less pronounced as commonly observed. In the shear thinning regime, depolarized SALS reveals an unexpectedly strong variation of the MLV size. SANS experiments using the samples with Lamellar contrast reveal a change in interLamellar spacing of up to 30% at stresses that lead to MLV formation. This change is much more pronounced than the change observed, when shear suppresses thermal bilayer undulations. MicroPhase separation occurs, and as a consequence, the Lamellar spacing decreases drastically. The coincidence of the change in Lamellar spacing and the onset of MLV formation is a strong indication for a morphology-driven microPhase separation.
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Shear-induced orientations in a lyotropic defective Lamellar Phase
Europhysics Letters (EPL), 1998Co-Authors: Jörg Berghausen, Johannes Zipfel, Peter Lindner, Walter RichteringAbstract:The influence of shear on a defective Lamellar Phase of the ternary mixture sodium dodecyl sulphate/decanol/D2O was studied using small-angle neutron scattering (SANS), small-angle light scattering (SALS) and birefringence. Shear flow leads to an alignment of lamellae but in addition to previous studies, we found a reorientation from "perpendicular" lamellae, i.e. with the layer normal along the vorticity direction, to "parallel" lamellae with the layer normal along the velocity gradient direction at increasing shear rates. The reorientation processes were accompanied by a decrease of viscosity.
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rheo small angle light scattering investigation of shear induced structural changes in a lyotropic Lamellar Phase
Journal of Colloid and Interface Science, 1996Co-Authors: Jörg Läuger, Richard Weigel, Klaus Berger, Karl Hiltrop, Walter RichteringAbstract:The influence of shear on a Lamellar Phase in the system sodium dodecyl sulfate/decanol/water was investigated by combined rheo-small angle light scattering. Three different regions were detected and all could be characterized by different scattering patterns in depolarized and polarized light scattering. Flow alignment of anisotropic domains in flow direction was found at low and high shear rates. A viscosity maximum was observed at intermediate shear rates, and different anisotropic scattering patterns were detected in polarized and depolarized scattering. The data are interpreted by a shear-induced formation of vesicles which displayed a characteristic four-lobe pattern in depolarized scattering. A butterfly pattern observed in polarized scattering indicated the existence of concentration fluctuations along the flow direction. The transitions between the three regions were reversible, but the formation of vesicles was found only when the sample was sheared for a long time at appropriate shear rates. Complicated rheological properties as, e.g., shear thinning and shear thickening, were found as a consequence of the structural changes.
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Anisotropic Small Angle Light and Neutron Scattering from a Lyotropic Lamellar Phase under Shear
Journal de Physique II, 1996Co-Authors: Richard Weigel, Walter Richtering, Jörg Läuger, Peter LindnerAbstract:The influence of shear on the Lamellar Phase of a semi-dilute solution (36% (w/w)) of tetra ethylenglycol dodecylether (CH3[ CH2] 11[ OCH2CH2] 4OH, C12E4) in water was investigated by Small Angle Light Scattering (SALS), Small Angle Neutron Scattering (SANS) and rheology. A plateau modulus was determined by low amplitude oscillatory shear experiments. A strong scattering peak perpendicular to the flow direction and a small peak along the flow direction were observed in rheo-SANS. The rheo-SALS patterns were also anisotropic. At low shear rates, a four lobe pattern was found in depolarized light scattering (HV) and scattering perpendicular to the flow direction was observed in polarized scattering (HH). A butterfly pattern was found in light scattering at high shear rates. The butterfly pattern was stable after cessation of shear, but it was changed by slow shear flow. The scattering data can be explained by a shear induced formation of deformed vesicles and the butterfly pattern might be correlated with an assembly of vesicles disordered in the direction of shear.
Didier Roux - One of the best experts on this subject based on the ideXlab platform.
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oscillating viscosity in a lyotropic Lamellar Phase under shear flow
Physical Review Letters, 2001Co-Authors: Annesophie Wunenburger, Jacques Leng, Annie Colin, A Arneodo, Didier RouxAbstract:We report some time-dependent behavior of lyotropic Lamellar Phase under shear flow. At fixed stress, near a layering instability, the system presents an oscillating shear rate. We build up a new stress versus shear rate diagram that includes temporal behavior. This diagram is made of two distinct branches of stationary states which correspond, respectively, to disordered and ordered multiLamellar vesicle Phases. When increasing the shear stress, prior to the transition to the ordered structural state, sustained oscillations of the viscosity are recorded. They correspond to periodic structural change of the entire sample between a disordered and a ordered state of multiLamellar vesicles.
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Swelling kinetics of a compressed Lamellar Phase
European Physical Journal E: Soft matter and biological physics, 2001Co-Authors: Jacques Leng, Frédéric Nallet, Didier RouxAbstract:We investigate how multiLamellar vesicles prepared in a compressed state under flow return to equilibrium. The kinetics is studied by following the temporal evolution of the viscoelasticity after the shear is stopped. It exhibits a two-step relaxation whose slower stage is strongly affected by temperature. According to a simple model, the temperature-dependent permeability of the Lamellar Phase is deduced from the measurements. We propose to attribute the permeability to handle-like defects, and its temperature dependence to an increase of the defect density when the Lamellar-to-sponge Phase transition is approached.
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structure of a lyotropic Lamellar Phase under shear
Physical Review Letters, 1997Co-Authors: Philippe Sierro, Didier RouxAbstract:The effect of shear on a lyotropic Lamellar Phase is studied by the means of small-angle light scattering and direct microscopic observations. We found a complex behavior that can be described by a shear diagram. This diagram exhibits successively as a function of shear four different steady states. After a transition to a Phase of monodisperse multiLamellar vesicles with no long-range order there is a transition to the same vesicles exhibiting long-range order. At even higher shear rates, there is a transition between this ordered population of vesicles of size typically $1\ensuremath{\mu}\mathrm{m}$ to another ordered state made of vesicles which are much bigger (from 10 to $50\ensuremath{\mu}\mathrm{m}$).
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effect of shear on a lyotropic Lamellar Phase
Journal De Physique Ii, 1993Co-Authors: Olivier Diat, Didier Roux, Frédéric NalletAbstract:We present a series of experiments, using different techniques such as light scattering, conoscopy, neutron scattering and microscopic observations, to determine the orientation of lyotropic Lamellar Phases under shear. Three states of orientation are observed, depending upon both the shear rate and the inter-membrane separation. These steady states are separated by dynamic transitions. Among the states described, we focus our attention on a state made of monodisperse close-packed multilayered vesicles whose size is precisely fixed by the shear rate.
Jean-baptiste Salmon - One of the best experts on this subject based on the ideXlab platform.
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shear banding in a lyotropic Lamellar Phase i time averaged velocity profiles
Physical Review E, 2003Co-Authors: Jean-baptiste Salmon, S. Manneville, Annie ColinAbstract:Using velocity profile measurements based on dynamic light scattering and coupled to structural and rheological measurements in a Couette cell, we present evidences for a shear-banding scenario in the shear flow of the onion texture of a lyotropic Lamellar Phase. Time-averaged measurements clearly show the presence of structural shear-banding in the vicinity of a shear-induced transition, associated to the nucleation and growth of a highly sheared band in the flow. Our experiments also reveal the presence of slip at the walls of the Couette cell. Using a simple mechanical approach, we demonstrate that our data confirms the classical assumption of the shear-banding picture, in which the interface between bands lies at a given stress $\sigma^\star$. We also outline the presence of large temporal fluctuations of the flow field, which are the subject of the second part of this paper [Salmon {\it et al.}, submitted to Phys. Rev. E].
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Shear-banding in a lyotropic Lamellar Phase, Part 2: Temporal fluctuations
Physical Review E : Statistical Nonlinear and Soft Matter Physics, 2003Co-Authors: Jean-baptiste Salmon, S. Manneville, A. ColinAbstract:We analyze the temporal fluctuations of the flow field associated to a shear-induced transition in a lyotropic Lamellar Phase: the layering transition of the onion texture. In the first part of this work [Salmon et al., submitted to Phys. Rev. E], we have evidenced banded flows at the onset of this shear-induced transition which are well accounted for by the classical picture of shear-banding. In the present paper, we focus on the temporal fluctuations of the flow field recorded in the coexistence domain. These striking dynamics are very slow (100--1000s) and cannot be due to external mechanical noise. Using velocimetry coupled to structural measurements, we show that these fluctuations are due to a motion of the interface separating the two differently sheared bands. Such a motion seems to be governed by the fluctuations of $\sigma^\star$, the local stress at the interface between the two bands. Our results thus provide more evidence for the relevance of the classical mechanical approach of shear-banding even if the mechanism leading to the fluctuations of $\sigma^\star$ remains unclear.
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Shear-banding in a lyotropic Lamellar Phase, Part 1: Time-averaged velocity profiles
Physical Review E : Statistical Nonlinear and Soft Matter Physics, 2003Co-Authors: Jean-baptiste Salmon, S. Manneville, A. ColinAbstract:Using velocity profile measurements based on dynamic light scattering and coupled to structural and rheological measurements in a Couette cell, we present evidences for a shear-banding scenario in the shear flow of the onion texture of a lyotropic Lamellar Phase. Time-averaged measurements clearly show the presence of structural shear-banding in the vicinity of a shear-induced transition, associated to the nucleation and growth of a highly sheared band in the flow. Our experiments also reveal the presence of slip at the walls of the Couette cell. Using a simple mechanical approach, we demonstrate that our data confirms the classical assumption of the shear-banding picture, in which the interface between bands lies at a given stress $\sigma^\star$. We also outline the presence of large temporal fluctuations of the flow field, which are the subject of the second part of this paper [Salmon {\it et al.}, submitted to Phys. Rev. E].
Ulf Olsson - One of the best experts on this subject based on the ideXlab platform.
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rheochaos and flow instability phenomena in a nonionic Lamellar Phase
Soft Matter, 2013Co-Authors: Bruno F B Silva, Luigi Gentile, Sebastian Lages, Kell Mortensen, J Kohlbrecher, Ulf OlssonAbstract:In this study we report on instability phenomena in a solution where shear induces multiLamellar vesicles (MLVs) from a Lamellar Phase. A shear-thickening regime has been observed for hexadecyl tetraethylene glycol ether (C16E4) dissolved in D2O at 40 °C. In this regime, unstable temporal viscosity behavior, i.e. periodic oscillations, has been observed at 2, 5 and 10 s−1. Moreover at a shear rate of 10 s−1 shear banding manifests itself as the occurrence of transparent and turbid bands stacked along the vorticity direction. We perform time-resolved-rheo-small angle neutron scattering (rheo-SANS) experiments to understand the nature of the viscosity oscillations and spatial-resolved experiments to obtain a structural characterization of vorticity bands.
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shear induced transitions between a planar Lamellar Phase and multiLamellar vesicles continuous versus discontinuous transformation
Langmuir, 2008Co-Authors: Bruno Medronho, Ulf Olsson, Maria G. Miguel, S Shafaei, R Szopko, Claudia SchmidtAbstract:The shear-induced transitions between an oriented Lamellar Phase and shear-induced multiLamellar vesicles (MLVs) in a nonionic surfactant system were studied by deuterium rheo-NMR spectroscopy as a function of time in start-up experiments at several temperatures and shear rates. By starting from an initial state of oriented lamellae and observing the transformation to the final steady state of MLVs and vice-versa, two different mechanisms were found, depending on the direction of the transition and the initial state. The transition is continuous when MLVs are formed, starting from the oriented Lamellar Phase. On the other hand, a discontinuous nucleation-and-growth process with a coexistence region is observed when transforming MLVs into an oriented Lamellar Phase.
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temperature induced dna compaction in a nonionic Lamellar Phase
Progress in colloid and polymer science, 2008Co-Authors: Alfredo Gonzalezperez, Ulf Olsson, Sanja Bulut, Bjorn LindmanAbstract:A nonionic Lamellar Phase was prepared using C10E3 in buffer solution at pH = 7.6. A suitable T4DNA concentration around 5 wt % was immobilized in a Lamellar Phase with 40 wt % C10E3. The mixed system was investigated at two temperatures, 25 and 5 °C by using cryo-fracture TEM direct imaging, fluorescence microscopy and small-angle X-ray scattering. The surprising results where obtained showing that the DNA conformation can be tuned to compacted and extended state at 25 and 5 °C, respectively. Additionally, DNA is aligned with a preferential orientation in the direction of the flow by simply injecting the sample in a capillary.
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Lamellar miscibility gap in a binary catanionic surfactant water system
Journal of Physical Chemistry B, 2007Co-Authors: Bruno F B Silva, Eduardo F Marques, Ulf OlssonAbstract:The coexistence of two Lamellar liquid-crystalline Phases in equilibrium for binary surfactant−water systems is a rare and still puzzling phenomenon. In the few binary systems where it has been demonstrated experimentally, the surfactant is invariably ionic and the miscibility gap is thought to stem from a subtle balance between attractive and repulsive interbilayer forces. In this paper, we report for the first time a miscibility gap for a catanionic Lamellar Phase formed by the surfactant hexadecyltrimethylammonium octylsulfonate (TASo) in water. Synchrotron small-angle X-ray scattering, polarizing light microscopy, and 2H NMR unequivocally show the coexistence of a dilute (or swollen) Lamellar Phase, Lα‘, and a concentrated (or collapsed) Lamellar Phase, Lα‘ ‘. Furthermore, linear swelling is observed for each of the Phases, with the immiscibility region occurring for 15−54 wt % surfactant. In the dilute region, the swollen Lamellar Phase is in equilibrium with an isotropic micellar region. Vesicles ca...
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Viscoelasticity of a nonionic Lamellar Phase.
Langmuir, 2007Co-Authors: Bruno Medronho, Maria G. Miguel, Ulf OlssonAbstract:The linear viscoelastic properties of a nonionic Lamellar Phase in C-orientation were studied as a function of temperature by small-amplitude oscillatory measurements in the frequency range 0.5−5 Hz. An almost solidlike elastic response was observed at all studied temperatures, from 42 to 20 °C. In this range, the elastic modulus was found to increase strongly with decreasing temperature. The elasticity is attributed to screw dislocations connecting layers in the stack, and the data thus suggest that the density of screw dislocations decreases with increasing temperature. The Lamellar Phase forms an “onion” texture when continuously sheared at lower temperatures. It is argued that a possible origin for the shear-induced “onion” texture is the instability of the screw dislocations in shear flow. By 2H NMR experimentation, we also find the formation of a random mesh Phase at lower temperatures. The presence of equilibrium bilayer perforations, however, does not correlate with the “onion” stability.
Annie Colin - One of the best experts on this subject based on the ideXlab platform.
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shear banding in a lyotropic Lamellar Phase i time averaged velocity profiles
Physical Review E, 2003Co-Authors: Jean-baptiste Salmon, S. Manneville, Annie ColinAbstract:Using velocity profile measurements based on dynamic light scattering and coupled to structural and rheological measurements in a Couette cell, we present evidences for a shear-banding scenario in the shear flow of the onion texture of a lyotropic Lamellar Phase. Time-averaged measurements clearly show the presence of structural shear-banding in the vicinity of a shear-induced transition, associated to the nucleation and growth of a highly sheared band in the flow. Our experiments also reveal the presence of slip at the walls of the Couette cell. Using a simple mechanical approach, we demonstrate that our data confirms the classical assumption of the shear-banding picture, in which the interface between bands lies at a given stress $\sigma^\star$. We also outline the presence of large temporal fluctuations of the flow field, which are the subject of the second part of this paper [Salmon {\it et al.}, submitted to Phys. Rev. E].
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oscillating viscosity in a lyotropic Lamellar Phase under shear flow
Physical Review Letters, 2001Co-Authors: Annesophie Wunenburger, Jacques Leng, Annie Colin, A Arneodo, Didier RouxAbstract:We report some time-dependent behavior of lyotropic Lamellar Phase under shear flow. At fixed stress, near a layering instability, the system presents an oscillating shear rate. We build up a new stress versus shear rate diagram that includes temporal behavior. This diagram is made of two distinct branches of stationary states which correspond, respectively, to disordered and ordered multiLamellar vesicle Phases. When increasing the shear stress, prior to the transition to the ordered structural state, sustained oscillations of the viscosity are recorded. They correspond to periodic structural change of the entire sample between a disordered and a ordered state of multiLamellar vesicles.
