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AUTO-STRUCTURATION DE PARTICULES MAGNETIQUES DANS UN CRISTAL LIQUIDE NEMATIQUE : VERS UN NOUVEAU TYPE DE COMPOSITE ADAPTATIF

Abstract : This work is relative to the self-structuring of magnetic particles in a nematic liquid crystal (NLC) matrix. The elaboration of new materials, combining magnetic properties and particles structuring, is part of the full expansion field of the research of adaptive materials. P. Poulin, the first, reported on new colloidal interactions induced by the elasticity of a nematic suspending fluid. To obtain a controlled structuring of micronic particles by the nematic matrix, an accurate control of the anchorage of the NLC molecules on the iron particles surface is necessary. Thus, after a thorough characterization of the state of the iron surface, various treatments, which ensure a homeotropic anchoring of the nematogens in contact with that surface, have been realized on plates used as model system. Two approaches have been explored: the first consists in modifying the iron surface state, the other one, much more promising, consists in modifying the surface by deposition of amphiphilic molecules. These treatments, successfully transposed to the iron particles, allow us to obtain strong homeotropic anchorage. This is absolutely necessary to create the topological defects inducing the self-alignment of the particles. The magnetic response of the iron particles under external field, observed by optical microscopy, allows us to calculate precisely, thanks to a finite elements method of magnetic force calculation, both the repulsive and the attractive contributions to the force. Then the complete profile of this force, due to the distortions of the NLC around the particles, for the first time, is built.
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https://tel.archives-ouvertes.fr/tel-00011071
Contributor : Céline Noel <>
Submitted on : Monday, November 21, 2005 - 5:11:24 PM
Last modification on : Monday, October 12, 2020 - 10:27:38 AM

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  • HAL Id : tel-00011071, version 1

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Céline Noel. AUTO-STRUCTURATION DE PARTICULES MAGNETIQUES DANS UN CRISTAL LIQUIDE NEMATIQUE : VERS UN NOUVEAU TYPE DE COMPOSITE ADAPTATIF. Matériaux. Université Nice Sophia Antipolis, 2005. Français. ⟨tel-00011071⟩

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