Bending moduli of a nonadsorbing-polymer-containing lyotropic lamellar phase: An experimental study

Bouglet, G.; Ligoure, Christian; Bellocq, A. M.; Dufourc, Érick J.; Mosser, Gervaise

doi:10.1103/physreve.57.834

Cited by 41 publications

(42 citation statements)

References 18 publications

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“…There are no general methods for determining these elastic constants; moreover, many of the methods in the literature probe and at length scales much larger than those relevant to sub-m vesicles (15)(16)(17)(18)(19). is especially difficult to measure as it influences topological transformations between structures such as the number and genus of objects [such as the distribution of material between vesicles (3,12), the size and distribution of various defect structures (18,19), or the transition between lamellar and L 3 phases (13, 14)] and does not influence the more readily measured fluctuations of the structure (12,13,15). A key requirement to the understanding and possible control of surfactant structural organization is developing both experimental and theoretical tools to relate R o , , and to surfactant molecular structure and solution conditions (9,12,15,20).…”

Section: ͪͬ [1]mentioning

confidence: 99%

Gaussian curvature and the equilibrium among bilayer cylinders, spheres, and discs

Jung

Lee

Kaler

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

138

172

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In mixtures of cetyltrimethylammonium bromide (CTAB) and sodium perfluorooctanoate (FC 7) in aqueous solution, novel bilayer cylinders with hemispherical end caps and open, flat discs coexist with spherical unilamellar vesicles, apparently at equilibrium. Such equilibrium among bilayer cylinders, spheres, and discs is only possible for systems with a spontaneous curvature, R o, and a positive Gaussian curvature modulus, . We have measured the size distributions of the spherical vesicles, cylinders, and discs by using cryo-electron microscopy; a simple analysis of this length distribution allows us to independently determine that the mean curvature modulus, Ϸ 5 ؎ 1 kBT and Ϸ 2 ؎ 1 kBT. This is one of the few situations in which R o, , and can be determined from the same experiment. From a similar analysis of the disk size distribution, we find that the edges of the discs are likely stabilized by excess CTAB. The fraction of discs, spherical vesicles, and cylinders depends on the CTAB͞FC 7 mole ratio: increasing CTAB favors discs, while decreasing CTAB favors cylinders. This control over aggregate shape with surfactant concentration may be useful for the design of templates for polymerization, mesoporous silicates, etc.cryogenic transmission electron microscopy ͉ surfactants ͉ vesicles T he starting point for the description of bilayer organization in solution is the harmonic approximation to the bending free energy (1):R 1 and R 2 are the principle radii of curvature of the structures, R o is the spontaneous radius of curvature, and are the mean and Gaussian curvature elastic constants, respectively, and A is the area of the bilayer membrane. The harmonic approximation is appropriate when the membrane thickness (1-3) [here Ϸ3 nm (4)] and the Debye length for ionic surfactants (2, 5, 6) [also Ϸ1-3 nm (4)] are small compared with R 1 and R 2 (Ϸ20-30 nm, see Fig. 1). The differences of the bending free energy, F B , of different aggregate geometries can often be of the order of k B T, leading to the possibility of multiple structures in equilibrium.The two elastic constants, and , play very different roles in determining bilayer organization. The magnitude of reflects the energy needed to bend the bilayer away from its spontaneous radius of curvature, R o . For ϳ k B T, thermal fluctuations give rise to significant curvature fluctuations, which lead to a net repulsive interaction between bilayers at short distances. This steric repulsion can stabilize unilamellar vesicles over multilamellar liposomes (3,4,7,8). Larger values of (ӷk B T), combined with a spontaneous curvature that picks out a particular vesicle radius, lead to unilamellar vesicles as the curvature variations inherent to multilamellar structures are energetically prohibited (3,4,9). A spontaneous bilayer curvature (1͞R o 0) is only possible when nonideal surfactant mixing causes the interior and exterior monolayers of the vesicle bilayer to have different compositions or environments (3, 10, 11).influences only the topology (and hence the number) of t...

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Section: ͪͬ [1]mentioning

confidence: 99%

Gaussian curvature and the equilibrium among bilayer cylinders, spheres, and discs

Jung

Lee

Kaler

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

138

172

View full text Add to dashboard Cite

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“…Among these interactions, the dominant repulsive forces which stabilize an expanded lamellar structure are the electrostatic interaction (for ionic systems) and the undulation or Helfrich's interaction [2]. Nowadays increasing interest is directed towards ternary lamellar systems of surfactant, water and polymer [3][4][5][6][7][8][9][10][11][12][13][14]. Previous studies have shown that added macromolecules (guest component of the lamellar phase) can occupy a variety of sites in such systems.…”

Section: Introductionmentioning

confidence: 99%

Polymer-mediated interactions of fluid membranes in a lyotropic lamellar phase: a small angle X-ray and neutron scattering study

Bouglet

Ligoure

1999

Eur. Phys. J. B

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Small angle X-ray and neutron scattering data on an effective three-component lamellar phase composed of water, a non adsorbing water-soluble polymer (polyvynilpyrolidone), fluid membranes, made from a mixture of a cationic surfactant (cetylpiridiumchloride) and a cosurfactant (hexanol), are presented for various membrane as well as polymer concentrations. The data are fitted with a recently proposed model which takes into account the geometry and the fluctuations of these periodic structures. This allows a quantitative study of the polymer contribution to the smectic compression modulusB of the lamellar phase. Four different regimes of polymer confinement are expected. The associated variations inB are compared to a recent theoretical model, which predicts the polymer-mediated contribution to the smectic compression modulus.

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“…Polymers grafted to the bilayers can induce gelation [4] or other phase changes [5,6] in liquid lamellar phases. They stabilize monodisperse vesicles [7] and modify the geometry of monolamellar [8,9] and multilamellar cylindrical vesicles [10].…”

Section: Introductionmentioning

confidence: 99%

Local entropic effects of polymers grafted to soft interfaces

Bickel

Jeppesen

Marques

2001

The European Physical Journal E

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In this paper, we study the equilibrium properties of polymer chains end-tethered to a fluid membrane. The loss of conformational entropy of the polymer results in an inhomogeneous pressure field that we calculate for gaussian chains. We estimate the effects of excluded volume through a relation between pressure and concentration. Under the polymer pressure, a soft surface will deform. We calculate the deformation profile for a fluid membrane and show that close to the grafting point, this profile assumes a cone-like shape, independently of the boundary conditions. Interactions between different polymers are also mediated by the membrane deformation. This pair-additive potential is attractive for chains grafted on the same side of the membrane and repulsive otherwise.

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Bending moduli of a nonadsorbing-polymer-containing lyotropic lamellar phase: An experimental study

Cited by 41 publications

References 18 publications

Gaussian curvature and the equilibrium among bilayer cylinders, spheres, and discs

Gaussian curvature and the equilibrium among bilayer cylinders, spheres, and discs

Polymer-mediated interactions of fluid membranes in a lyotropic lamellar phase: a small angle X-ray and neutron scattering study

Local entropic effects of polymers grafted to soft interfaces

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