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Défauts d'équilibre des phases ordonnées et structure du liquide isotrope d'un mélange lyotrope de surfactant non-ionique

Abstract : The first part of this work concerned the study of the pretransitional effects that appear upon heating in the ordered phases of the binary lyotropic mixture C12EO6/H2O on approaching the transition towards the isotropic phase. Using a photobleaching technique, we measured the diffusion constants of fluorescent dyes as a function of temperature. We showed that structural defects connecting the surfactant structure appear in the lamellar and hexagonal phases and determined their structure and density. We inferred that the isotropic phase itself is highly connected close to the mesophases. This conclusion is supported by the fact that the diffusion constant does not vary at the transition between the isotropic and cubic bicontinuous phases.

We then explored the dynamical properties of the isotropic phase at high concentration using both high-frequency rheology and dynamic light scattering techniques. We find an extremely short (in the microsecond range) terminal relaxation time that we explain in the light of already existing theories on the flow behaviour of connected micelles taking into account the effect of local order.
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https://tel.archives-ouvertes.fr/tel-00010863
Contributor : Doru Constantin <>
Submitted on : Friday, November 4, 2005 - 1:26:03 PM
Last modification on : Thursday, November 21, 2019 - 2:21:56 AM
Long-term archiving on: : Friday, September 14, 2012 - 3:25:31 PM

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  • HAL Id : tel-00010863, version 1

Citation

Doru Constantin. Défauts d'équilibre des phases ordonnées et structure du liquide isotrope d'un mélange lyotrope de surfactant non-ionique. Dynamique des Fluides [physics.flu-dyn]. Ecole normale supérieure de lyon - ENS LYON, 2002. Français. ⟨tel-00010863⟩

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