Undulation instability of lamellar phases under shear: A mechanism for onion formation?

Zilman, Anton; Granek, Rony

doi:10.1007/s100510051187

Cited by 115 publications

(120 citation statements)

References 27 publications

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“…The local molecular mechanisms involved in the changes of the MLV size are still far from understood. The transition from planar lamellae to a phase of MLVs has been proposed to be a consequence of a mechanical flow instability of the planar lamellae at higher shear rates [40][41][42]. It remains to be shown how the reversibility of the MLV size, as demonstrated here, as well as the reversibility of the lamellar-MLV transition [32] fit into the picture of flow instabilities.…”

Section: Polarized Light Microscopymentioning

confidence: 70%

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: Polarized Light Microscopymentioning

confidence: 70%

Reversible size of shear-induced multi-lamellar vesicles

et al. 2005

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“…It would be required to incorporate the effect of the defect generation additionally to the Helfrich interaction. Actually it has been pointed out that the critical shear rate of the onion phase formation also shows remarkable discrepancy from the theoretical prediction that only considers the Helfirch interaction [6][7][8]16]. All of present issues concerning with the mechanism of the shear-induced onion phase and orientation transition seems to be attributed to the violation of the Helfrich stabilized lamellar phase due to defects.…”

Section: Resultsmentioning

confidence: 85%

“…Instability of the lamellar phase is explained by the Helfrich-Hurault mechanism [13][14][15][16][17]. The HelfrichHurault effect is undulation instability of the smectic phase subjected to the external electric or magnetic field [17].…”

Section: Introductionmentioning

confidence: 99%

“…Thus reduced repulsive force generates effective dilation along the layer normal of the membrane in order to retain the equilibrium layer spacing. It has been anticipated that, as the dilation becomes larger than the critical value, coherent buckling of the lamellar membranes appears and either the onion phase formation or the layer orientation is eventually triggered [13][14][15][16]. However, experimental observations present that the onion phase formation and the layer orientation transition occur in different shear rate range [1,4,5].…”

Section: Introductionmentioning

confidence: 99%

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Orientation transition of defective lyotropic triblock copolymer lamellar phase

Fujii

Yamämoto

2014

J Biorheol

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We study concentration dependence of the critical shear rate of a layer orientation transition in lyotropic triblock copolymer lamellar phase. Theory predicts that suppression of undulation fluctuation by shear triggers the transition. The critical shear rate at high polymer concentration is in reasonable agreement with theory. However, experimental results at low polymer concentrations show different behavior from the prediction. Violation of the theory is attributed to defective nature of the lamellar phase, in which creation of defects prevents the suppression of the undulation fluctuation.

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“…Zilman and Granek theoretically proposed a buckling mechanism for the onion formation [6]. In their model, the buckling of membranes is induced by effective lateral pressure which is generated by suppression of short wavelength undulation under shear.…”

Section: Introductionmentioning

confidence: 99%

Structural rheology of composite onion phase

Fujii

2015

J Biorheol

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We study the shear-induced composite onion phase formation behavior of the nonionic surfactant C 10 E 3 lamellar phases containing colloidal particles. Composite lamellar phase gives rise to the onion phase similar to the free-particle system. Depending on the particle size and concentration, the nonlinear rheology and shear modulus are significantly influenced, while the critical shear rate and onion formation kinetics remains unchanged from those of the free-particle system. Modification of the nonlinear rheology indicates that the colloidal particles assist the onion structure formation so that undulation instability is easily induced by anchoring of membranes on surface of particles. The shear modulus of the composite lamellar and onion phases is reasonably explained by considering the line tension of defects and the effect of polyhedral edge of the onion, respectively.

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Undulation instability of lamellar phases under shear: A mechanism for onion formation?

Abstract: PACS. 64.70.Md Transitions in liquid crystals, 61.30.Jf Defects in liquid crystals, 68.10.Et Interface elasticity, viscosity, and viscoelasticity,

Cited by 115 publications

References 27 publications

Reversible size of shear-induced multi-lamellar vesicles

Reversible size of shear-induced multi-lamellar vesicles

Orientation transition of defective lyotropic triblock copolymer lamellar phase

Structural rheology of composite onion phase

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