Cristaux liquides cholestériques en conditions non usuelles de photogélification: modulation du profil de réflexion de la lumière

Abstract : Due to their helical structure, Cholesteric Liquid Crystals (CLC) selectively reflect light. The central wavelength λ0 of the reflected light is proportional to the helical pitch, and its bandwidth is equal to a few tens of nanometres around λ0. Moreover, the amount of reflected light is limited to 50% of the incident non polarized light.

This PhD research work was centred on atypical reflection properties of CLC gels, with two different directions: the broadening of the bandwidth and the increase of the reflected light flux.

The first part of the manuscript presents an elaboration process which permits to enlarge the bandwidth of CLC gels. This is achieved by taking advantage of the natural UV light absorbing properties of a CLC, leading to a UV intensity gradient during the photoinduced elaboration of the gel. Optical microscopy, spectroscopy and transmission electron microscopy investigations permitted to determine the structural distribution of the polymer network at the origin of the observed reflected light distribution.

The second part is dedicated to the increase of the amount of the light reflected by a CLC gel, using a CLC whose helical sense varies with temperature. The impact of the polymerisation history and of the variation of temperature after gelation on the reflection properties are analysed, with a special emphasis on the nature and the quantity of polarisation of the reflected light.
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https://tel.archives-ouvertes.fr/tel-00179999
Contributor : Sabrina Relaix <>
Submitted on : Thursday, November 15, 2007 - 5:26:01 PM
Last modification on : Monday, April 29, 2019 - 5:28:52 PM
Long-term archiving on : Friday, November 25, 2016 - 5:36:36 PM

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  • HAL Id : tel-00179999, version 2

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Sabrina Relaix. Cristaux liquides cholestériques en conditions non usuelles de photogélification: modulation du profil de réflexion de la lumière. Physique [physics]. Université Paul Sabatier - Toulouse III, 2007. Français. ⟨tel-00179999v2⟩

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