Crumpling and second sound in lyotropic lamellar phases

Lubensky, T. C. ; Prost, J. ; Ramaswamy, S. (1990) Crumpling and second sound in lyotropic lamellar phases Journal de Physique Archives, 51 (10). pp. 933-943. ISSN 1155-4320

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We study relative concentration fluctuations in two component lamellar smectic liquid crystals consisting of surfactant layers of width w separated by a background fluid and show that these fluctuations are dominated by crumpling fluctuations of the surfactant layers when (w/l)2 <<; 1 where f is the average layer spacing. Our results are based on generalizations of the Helfrich theory in which the crumpling ratio k-2, densities πs and πb of the surfactant and background fluid, and w as well as l are allowed to vary. In the incompressible limit with πs, πb and w fixed, concentration fluctuations at constant f are determined entirely by fluctuations in k-2 . In this limit, the ratio of the high-frequency, constant concentration compressibility modulus B to the low-frequency, constant chemical potential modulus B is of order (κ /T)2 (l-ω) 2/l2 where k is the layer bending rigidity and T is the temperature. We show that corrections to the incompressible limit arising from fluctuations in w are of relative order (ω/l)2 (κ/U) where U is a molecular energy.

Item Type:Article
Source:Copyright of this article belongs to EDP Science.
Keywords:Compressibility of Liquids; Elasticity of Liquids; Fluctuations; Liquid Structure; Second Sound; Smectic Liquid Crystals
ID Code:40136
Deposited On:21 May 2011 10:04
Last Modified:21 May 2011 10:05

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