Dilute and concentrated phases of vesicles at thermal equilibrium

Hervé, Pascal; Roux, D.; Bellocq, A. M.; Nallet, Frédéric; Gulik-Krzywicki, T.

doi:10.1051/jp2:1993196

Cited by 118 publications

(160 citation statements)

References 16 publications

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“…The corresponding lamellar phase is a made of sodium dodecylsulphate, octanol and brine (respectively, 7, 8, 85% in weight with 20 g/l of NaCl in water, in the present study -see Ref. [14] for a phase diagram). Under a steady shear flow, the behaviour is strongly temperature sensitive and a shear diagram in the plane (T,γ) has been built [11].…”

Section: Effect Of Shear On Lyotropic Lamellar Phasesmentioning

confidence: 90%

Anomalous elasticity of an ordered lamellar liquid foam

Leng¹,

Nallet²,

Roux³

2001

The European Physical Journal E

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Abstract. We investigate experimentally the linear viscoelastic properties of a lamellar liquid foam as a function of the cell size and spatial organisation. The system consists of multilamellar vesicles generated by a simple shear flow on a lyotropic lamellar phase. The vesicles can be prepared either in an amorphous or a spatially ordered state. Their size is easily tunable in the range R = 0.5-15 µm. Whereas the shear modulus of the amorphous lamellar foam is alike that of usual liquid foams or concentrated emulsions and scales linearly with 1/R, the elastic modulus of the ordered foam is almost independent of the cell size. This result -probably the first describing the elasticity of an ordered foam-like system-remains unexplained.

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Section: Effect Of Shear On Lyotropic Lamellar Phasesmentioning

confidence: 90%

Anomalous elasticity of an ordered lamellar liquid foam

Leng¹,

Nallet²,

Roux³

2001

The European Physical Journal E

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“…when is small, leading to stable unilamellar vesicles, especially when combined with electrostatic repulsion in charged systems (10)]. Theory and experiments have shown that surfactant mixing can lead to sufficiently low values of (10,19,20).…”

Section: ϫ2mentioning

confidence: 99%

“…This is important especially for differentiating between metastable mechanically or chemically formed unilamellar vesicles [the equilibrium form of which is often a multilayered lamellar phase (2) or multilayered liposomes (3,4)] and equilibrium unilamellar vesicles (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Unilamellar vesicles can be stabilized against formation of multilamellar liposomes by either (i) thermal fluctuations that lead to a net repulsive interaction between bilayers (18) or (ii) a spontaneous curvature that picks out a particular vesicle radius with other bilayer curvatures being prohibited energetically (7)(8)(9).…”

mentioning

confidence: 99%

The origins of stability of spontaneous vesicles

Jung¹

2001

Proceedings of the National Academy of Sciences

107

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Equilibrium unilamellar vesicles are stabilized by one of two distinct mechanisms depending on the value of the bending constant. Helfrich undulations ensure that the interbilayer potential is always repulsive when the bending constant, K, is of order k BT. When K Ͼ Ͼ k BT, unilamellar vesicles are stabilized by the spontaneous curvature that picks out a particular vesicle radius; other radii are disfavored energetically. We present measurements of the bilayer elastic constant and the spontaneous curvature, R o, for three different systems of equilibrium vesicles by an analysis of the vesicle size distribution determined by cryo-transmission electron microscopy and smallangle neutron scattering. For cetyltrimethylammonium bromide (CTAB)͞sodium octyl sulfonate catanionic vesicles, K ‫؍‬ .7 k BT, suggesting that the unilamellar vesicles are stabilized by Helfrich-undulation repulsions. However, for CTAB and sodium perfluorooctanoate (FC7) vesicles, K ‫؍‬ 6 kBT, suggesting stabilization by the energetic costs of deviations from the spontaneous curvature. Adding electrolyte to the sodium perfluorooctanoate͞CTAB vesicles leads to vesicles with two bilayers; the attractive interactions between the bilayers can overcome the cost of small deviations from the spontaneous curvature to form two-layer vesicles, but larger deviations to form three and more layer vesicles are prohibited. Vesicles with a discrete numbers of bilayers at equilibrium are possible only for bilayers with a large bending modulus coupled with a spontaneous curvature.

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“…The L α phase we studied is a quaternary mixture of sodium-dodecyl sulfate, octanol and brine (7%, 8%, 85% w/w, respectively, NaCl at 20 g/l) whose phase diagram has already been published [17]. This L α phase is stabilised by steric interactions [18] and its smectic period is d ≈ 160Å for this composition.…”

Section: The State Of Compressed Onionsmentioning

confidence: 99%

“…For instance, τ is a function of r 0 which is a priori not well defined but certainly of order of d 0 . Assuming r 0 = d 0 /2, the Helfrich expression forB with κ = 5k B T [17], R = 10 µm as given by light scattering, and the unknown numerical prefactor in equation (5) equal to 1 leads to figure 9. The surface density of defects increases sensibly with the temperature, although being small (φ s < 1%).…”

Section: Analysis: a Porous L α Phasementioning

confidence: 99%

Swelling kinetics of a compressed lamellar phase

Leng

Nallet

Roux

2001

The European Physical Journal E

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Abstract. 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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Dilute and concentrated phases of vesicles at thermal equilibrium

Cited by 118 publications

References 16 publications

Anomalous elasticity of an ordered lamellar liquid foam

Anomalous elasticity of an ordered lamellar liquid foam

The origins of stability of spontaneous vesicles

Swelling kinetics of a compressed lamellar phase

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