Elastic properties of polymer-doped dilute lamellar phases: A small-angle neutron scattering study |
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Authors: | M-F Ficheux A-M Bellocq F Nallet |
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Institution: | (1) Centre de recherche Paul-Pascal, CNRS, avenue du Docteur-Schweitzer, F-33600 Pessac, France, FR |
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Abstract: | We investigate experimentally, using small-angle neutron scattering the elastic properties of polymer-doped dilute lamellar
phases. In our system the polymer is water-soluble but nevertheless partially adsorbs onto the negatively charged surfactant
bilayers. The effective polymer-mediated interaction between bilayers is less repulsive than the weakly screened electrostatic
interaction that prevails at zero polymer content. It even becomes attractive in some regions of the phase diagram. Small-angle
neutron scattering allows us to measure directly the Caillé exponent η characterizing the bilayer fluctuations in lamellar
(smectic A) phases, and thus indirectly estimate the compression modulus as a measure of the strength of the bilayer-bilayer interactions. The compression modulus appears to be vanishing at a point
located on the lamellar-lamellar phase separation boundary, a candidate critical point.
Received: 7 August 2000 |
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Keywords: | PACS 82 70 -y Disperse systems – 68 10 -m Fluid surfaces and fluid-fluid interfaces – 05 40 -a Fluctuation phenomena random processes noise and Brownian motion |
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