J. Phys. II France
Volume 1, Numéro 9, September 1991
Page(s) 1121 - 1132
DOI: 10.1051/jp2:1991208
J. Phys. II France 1 (1991) 1121-1132

Fluid membranes in the "semi-rigid regime": scale invariance

M. Skouri, J. Marignan, J. Appell and G. Porte

Groupe de Dynamique des phases Condensées, USTL - Case 26, 34095 Montpellier Cedex 05, France

(Received 26 March 1991, accepted 23 May 1991)

We investigate here the swollen lamellar phase L $_\alpha$ and the anomalous isotropic (sponge) phase L 3 of the ternary system AOT/brine using neutron and light scattering. We first measure the excess area of bilayers from the deviations to the simple swelling behavior and so obtain an evaluation of the mean curvature rigidity K of the bilayers. K is found quite high $K \approx 3 k_{\rm B} T$ and is basically the same in both L $_\alpha$ and L 3. Correspondingly, the persistence length $\xi_{\rm K}$ of the bilayer is of the order of 10 6 ${\rm\AA}$ so that the samples are in the "semi-rigid regime" at all practical dilutions. The scale invariance of the statistics of the fluid bilayers expected for such regime is then checked by comparing the neutron and light scattering patterns of samples of different concentrations.

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