Steric Interaction of Fluid Membranes in Multilayer Systems

AbstractThe out-of-plane fluctuations of fluid membranes are sterically hindered in multilayer systems. The repulsive interaction associated with the steric or excluded-volume effect is studied theoretically by two methods. The interaction energy per unit area of membrane is derived as a function of temperature, membrane curvature elasticity and mean membrane spacing; it is inversely proportional to the square of the latter. Steric repulsion is estimated for lecithin bilayers in water. There and in other cases, it may compete with van der Waals attraction.

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Interplay Between the Repulsive and Attractive Interaction and the Spacial Dimensionality of an Excess Electron in a Simple Fluid

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633603000495 ◽

2003 ◽

Vol 02 (02) ◽

pp. 129-138

Author(s):

Ashok Sethia ◽

Eric R. Bittner ◽

Fumio Hirata

Keyword(s):

Three Dimensional ◽

Chem Phys ◽

Volume Effect ◽

Excess Electron ◽

Attractive Interaction ◽

Repulsive Interaction ◽

Solvated Electron ◽

Solvent Interaction ◽

Solvent Atom ◽

Excluded Volume Effect

The behavior of an excess electron in a one, two and three dimensional classical liquid has been studied with the aid of Chandler, Singh and Richardson (CSR) theory [J. Chem. Phys.81, 1975 (1984)]. The size or dispersion of the wavepacket associated with the solvated electron is very sensitive to the interaction between the electron and fluid atoms, and exhibits complicated behavior in its density dependence. The behavior is interpreted in terms of an interplay among four causes: the excluded volume effect due to solvent, the pair attractive interaction between the electron and a solvent atom, the thermal wavelength of the electron (λe), a balance of the attractive interactions from different solvent atoms and the range of repulsive interaction between electron and solvent atom. Electron self-trapping behavior in all the dimensions has been studied for the same solvent-solvent and electron-solvent interaction potential and the results are presented for the same parameter in every dimension to show the comparison between the various dimensions.

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Fluctuating Interfaces: a Series of Synchrotron X-Ray Scattering Studies of Interacting Stacked Membranes

MRS Proceedings ◽

10.1557/proc-143-9 ◽

1988 ◽

Vol 143 ◽

Cited By ~ 1

Author(s):

C. R. Safinya

Keyword(s):

Intrinsic Property ◽

Three Dimensions ◽

Repulsive Interaction ◽

Geometrical Shape ◽

Shear Moduli ◽

X Ray ◽

X Ray Scattering ◽

Fluid Membranes ◽

Out Of Plane ◽

Ray Scattering

AbstractIn this paper we concentrate on fluctuation phenomena encountered in interacting multilayered fluid membranes using synchrotron x-ray scattering as the primary tool. These systems consisting of surfactant or lipidic surfaces, are prototype models for understanding the statistical behavior of fluctuating surfaces embedded in three-dimensions. In elucidating the nature of fluid membranes we stress a unique intrinsic property: in contrast to usual surfaces with finite shear moduli, where surface tension plays a central role, the free energy of these essentially tensionless surfaces is governed by their geometrical shape and its fluctuations. We present data in a new regime of stability for very dilute and flexible membranes with interlayer separations of order hundreds of Angstroms. This is in contrast to most rigid membranes where the interlayer interactions are dominated by detailed microscopic interactions such as hydration and van der Waals. We show that the stability of these dilute lamellar phases is associated with violent out-of-plane fluctuations of the membranes giving rise to an effectively large long-range repulsive interaction theoretically elucidated by Helfrich. Because of its entropic origin, this interaction is universal and we present data for two different surfactant systems. Finally, we show that this new regime is distinct from the classical regime in which largely separated membrane sheets are stabilized because of their mutual electrostatic repulsion.

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