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Theses
Elaboration et caractérisations électro-optique et diélectrique de composites à cristaux liquides ferroélectriques dispersés dans une matrice polymère
Elaboration et caractérisations électro-optique et diélectrique de composites à cristaux liquides ferroélectriques dispersés dans une matrice polymère
Abstract : The ferroelectric liquid crystals have been the subject of a great interest in the last few years due to their application in the fast switching display devices. However, these devices present a low resistance against shocks and mechanical distortions. To resolve this problem, one of the suggested solutions is to disperse the liquid crystal in micro-droplets form within a polymer matrix. Such materials are called Polymer Dispersed Ferroelectric Liquid Crystal (PDFLC).
This work concerns the elaboration and the structural, dielectric and electro-optical characterizations of PDFLC films. Our main goal was to study the influence of the dispersed and the confined nature of the liquid crystal phase on these properties. Two ferroelectric liquid crystals with respectively a short and a large pitch compared to the droplets size were used to prepare these composites.
Very interesting electro-optic properties were found for composite films, like bistability, fast switching response, as well as low driving voltages. The relaxation modes observed for the composites were associated to ferroelectric properties of the liquid crystals. The characteristics of these processes are compared to those observed for the bulk ferroelectric liquid crystals. Some differences are underlined, as an important decrease of the strength of processes and an increase of their relaxation frequencies for composites, compared to bulk liquid crystals. These behaviours were explained by the dielectric heterogeneity of the composite films.
This work concerns the elaboration and the structural, dielectric and electro-optical characterizations of PDFLC films. Our main goal was to study the influence of the dispersed and the confined nature of the liquid crystal phase on these properties. Two ferroelectric liquid crystals with respectively a short and a large pitch compared to the droplets size were used to prepare these composites.
Very interesting electro-optic properties were found for composite films, like bistability, fast switching response, as well as low driving voltages. The relaxation modes observed for the composites were associated to ferroelectric properties of the liquid crystals. The characteristics of these processes are compared to those observed for the bulk ferroelectric liquid crystals. Some differences are underlined, as an important decrease of the strength of processes and an increase of their relaxation frequencies for composites, compared to bulk liquid crystals. These behaviours were explained by the dielectric heterogeneity of the composite films.
Cited literature [61 references]
https://tel.archives-ouvertes.fr/tel-00009656
Contributor : Frédéric Dubois <>
Submitted on : Thursday, July 7, 2005 - 6:40:14 PM
Last modification on : Monday, January 11, 2021 - 3:52:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:42:11 PM
Contributor : Frédéric Dubois <>
Submitted on : Thursday, July 7, 2005 - 6:40:14 PM
Last modification on : Monday, January 11, 2021 - 3:52:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:42:11 PM