Shear-induced orientations in a lyotropic defective lamellar phase

Berghausen, Jörg; Zipfel, J.; Lindner, Peter; Richtering, Walter

doi:10.1209/epl/i1998-00417-3

Cited by 76 publications

(66 citation statements)

References 20 publications

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“…In fact, many different shear effects have been reported: transformation from lamellar phases to Multi-lamellar vesicles, MLVs (or ''onions''), in different amphiphilic systems and followed by different techniques [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]; formation of MLVs in presence of submicron-size particles (''stuffed onions'') [21]; changes in lamellar orientation [17,22,23]; formation of intermediates with cylindrical structure between a lamellar and MLV phases [24][25][26]; reduction in lamellar spacing [27]; transitions from MLVs to unilamellar vesicles [28] and ''layering'' effects on onions [8,29]. As a practical application, these MLVs can be used, for instance, to encapsulate chemicals leading to a new kind of controlled micro-reactor [30] or as carriers for oligonucleotide delivery [31].…”

Section: Introductionmentioning

confidence: 99%

Reversible size of shear-induced multi-lamellar vesicles

et al. 2005

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IntroductionThe behavior of lamellar phases under shear is a subject that has been receiving a lot of attention in the recent years [1][2][3][4]. In fact, many different shear effects have been reported: transformation from lamellar phases to Multi-lamellar vesicles, MLVs (or ''onions''), in different amphiphilic systems and followed by different techniques [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]; formation of MLVs in presence of submicron-size particles (''stuffed onions'') [21]; changes in lamellar orientation [17,22,23]; formation of intermediates with cylindrical structure between a lamellar and MLV phases [24][25][26]; reduction in lamellar spacing [27]; transitions from MLVs to unilamellar vesicles [28] and ''layering'' effects on onions [8,29]. As a practical application, these MLVs can be used, for instance, to encapsulate chemicals leading to a new kind of controlled micro-reactor [30] or as carriers for oligonucleotide delivery [31].The size distribution of shear-induced multi-lamellar surfactant vesicles depends on the applied shear rate. In general, the MLV systems are shear thinning and the average MLV radius, R, decreases as the shear rate increases [5,26,32]. For higher surfactant concentrations, the inter-bilayer spacing is independent of the MLV size [33]. Hence, a decrease in the MLV size is accompanied by an increase in the MLV number density, N/V, where N is the number of vesicles and V the total volume. The MLVs at higher surfactant concentrations are polyhedral. They fill space with a total volume fraction which is essentially unity [8,34] and N/V is approximately proportional to R )3 . Abstract We have investigated the reversibility in the shear-induced multi-lamellar vesicle (MLV) size during stepwise cycling of the shear rate by employing common rheometry, polarized light microscopy and rheo-optic techniques. We thus address the question whether there is a true MLV steady state, irrespective of history. The system studied, was the nonionic surfactant triethylene glycol decyl ether (C 10 E 3 ) with a concentration of 40 wt.% in D 2 O and a constant temperature of 25°C. It was found that the MLV size varies reversibly with varying shear rate, and hence there exists a true steady state in the presence of shear flow. The experimental observations of reversibility are however restricted to higher shear rates. Because the transformation of the size results from the shear strain, the process is very slow at lower shear rates, where the steady state cannot be reached within a reasonable experimental time.

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Section: Introductionmentioning

confidence: 99%

Reversible size of shear-induced multi-lamellar vesicles

et al. 2005

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“…The effects of flow on lyotropic lamellar phases have been recently widely studied [1][2][3][4][5][6][7]. It has been shown that under shear some rearrangements of the lamellae occur which lead to well-defined steady-state orientations.…”

Section: Introductionmentioning

confidence: 99%

Undulation instability under shear: A model to explain the different orientations of a lamellar phase under shear?

Wunenburger

Colin

et al. 2000

Eur. Phys. J. E

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We study the effects of a dilation on a sheared smectic A phase. Through a linear analysis, we show that undulation may grow in the direction of the flow and of the vorticity as found in previous works. At higher shear rates, we evidence that the undulation along the flow disappears whereas it persists in the vorticity direction. We determine the stable or unstable zone as a function of the shear rate and of the lamellar spacing. This allows us to draw a theoretical shear diagram of the instability. Finally we compare our results with the orientations found experimentally in a lyotropic lamellar phase under shear. Our diagram describes qualitatively and quantitatively the transition observed at high shear rate.

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“…To design functional materials, one must understand the physical basis of the effects of molecular architecture and processing conditions (especially shear frequency, strain and temperature) on the rheological response of the liquid crystalline mesophases (Berghausen et al 1998;Rey & Denn 2002). The distribution of defects within a liquid crystal domain, defined as the 'texture' of the liquid crystal, plays a significant role in its rheology (Rey & Denn 2002).…”

Section: Large-scale Lb Simulations Of Liquid Crystalline Rheologymentioning

confidence: 99%

Real science at the petascale

Saksena

Boghosian

Fazendeiro

et al. 2009

Phil. Trans. R. Soc. A.

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We describe computational science research that uses petascale resources to achieve scientific results at unprecedented scales and resolution. The applications span a wide range of domains, from investigation of fundamental problems in turbulence through computational materials science research to biomedical applications at the forefront of HIV/AIDS research and cerebrovascular haemodynamics. This work was mainly performed on the US TeraGrid 'petascale' resource, Ranger, at Texas Advanced Computing Center, in the first half of 2008 when it was the largest computing system in the world available for open scientific research. We have sought to use this petascale supercomputer optimally across application domains and scales, exploiting the excellent parallel scaling performance found on up to at least 32 768 cores for certain of our codes in the so-called 'capability computing' category as well as highthroughput intermediate-scale jobs for ensemble simulations in the 32-512 core range. Furthermore, this activity provides evidence that conventional parallel programming with MPI should be successful at the petascale in the short to medium term. We also report on the parallel performance of some of our codes on up to 65 636 cores on the IBM Blue Gene/P system at the Argonne Leadership Computing Facility, which has recently been named the fastest supercomputer in the world for open science.

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Shear-induced orientations in a lyotropic defective lamellar phase

Cited by 76 publications

References 20 publications

Reversible size of shear-induced multi-lamellar vesicles

Reversible size of shear-induced multi-lamellar vesicles

Undulation instability under shear: A model to explain the different orientations of a lamellar phase under shear?

Real science at the petascale

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