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Proceedings Paper

Photochemical manipulation of colloidal structures in liquid-crystal colloids
Author(s): T. Yamamoto; Y. Tabe; H. Yokoyama
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Paper Abstract

We investigated photochemical manipulation of physical properties and colloidal structures in liquid-crystal (LC) colloids containing azobenzene compounds. In a LC suspension where polymeric particles were dispersed in a host LC, we achieved photochemical control of light-scattering properties of the suspension. In a nematic phase, when the suspension was sandwiched with two glass plates, the film became opaque. This would be attributable to an appearance of both multidomain structures of LC alignment and mismatches of refractive indices between the materials. The opaque state turned into a transparent one when a nematic-to-isotropic phase transition was induced by the trans-to-cis photoisomerization of the azo-dye. This will result from a disappearance of both the multidomain structures and the refractive-index mismatches in the isotropic phase. The transparent film went back into the initial opaque film when the nematic phase was obtained by the cis-to-trans photoisomerization. In a LC emulsion in which glycerol or water droplets were dispersed in liquid crystals, we examined photochemical change of defect structures and inter-droplet distances by the photochemical manner. At the initial state, Saturn ring and hedgehog defects were formed around the droplets. For the glycerol droplets, we observed structural transformations between Saturn ring and boojums on irradiation with ultra-violet and visible light. For the water droplets, the inter-droplet distances varied by changing defect size on the irradiation. These phenomena would result from modulation of anchoring conditions of the droplets by the photoisomerization of the azo-dyes.

Paper Details

Date Published: 9 May 2007
PDF: 13 pages
Proc. SPIE 6587, Liquid Crystals and Applications in Optics, 658707 (9 May 2007); doi: 10.1117/12.722656
Show Author Affiliations
T. Yamamoto, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (Japan)
Japan Science and Technology Agency (Japan)
Y. Tabe, Japan Science and Technology Agency (Japan)
Waseda Univ. (Japan)
H. Yokoyama, Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (Japan)
Japan Science and Technology Agency (Japan)


Published in SPIE Proceedings Vol. 6587:
Liquid Crystals and Applications in Optics
Milada Glogarova; Peter Palffy-Muhoray; Martin Copic, Editor(s)

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