LaPO4 Mineral Liquid Crystalline Suspensions with Outstanding Colloidal Stability for Electro-Optical Applications

Mineral liquid crystals are materials in which mineral's intrinsic properties are combined with the self‐organization behavior of colloids. However, the use of such a system for practical application, such as optical switching, has rarely been demonstrated due to the fundamental drawbacks of co...

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Bibliographic Details
Published in:Advanced functional materials 2012-12, Vol.22 (23), p.4949-4956
Main Authors: Kim, Jongwook, de la Cotte, Alexis, Deloncle, Rodolphe, Archambeau, Samuel, Biver, Claudine, Cano, Jean-Paul, Lahlil, Khalid, Boilot, Jean-Pierre, Grelet, Eric, Gacoin, Thierry
Format: Article
Language:English
Subjects:
colloids
electro-optical materials
lanthanum phosphate nanorods
liquid crystals
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Summary:Mineral liquid crystals are materials in which mineral's intrinsic properties are combined with the self‐organization behavior of colloids. However, the use of such a system for practical application, such as optical switching, has rarely been demonstrated due to the fundamental drawbacks of colloidal systems such as limited dispersion stability. Studying colloidal suspensions of LaPO4 nanorods, it is found that drastic improvement of colloidal stability can be obtained through a transfer of particles from water towards ethylene glycol, thus enabling the investigation of liquid crystalline properties of these concentrated suspensions. Using polarization microscopy and small‐angle x‐ray scattering (SAXS), self‐organization into nematic and columnar mesophases is observed enabling the determination of the whole phase diagram as a function of ionic strength and rod volume fraction. When an external alternative electric field is applied, a very efficient orientation of the nanorods in the liquid‐crystalline suspension is obtained, which is associated with a significant optical birefringence. These properties, combined with the high colloidal stability, are promising for the use of such high transparent and athermal material in electro‐optical devices. A new type of mineral liquid crystal system composed of LaPO4 particles with tuned long rod‐like morphology self‐organizes into different mesophases. An electro‐optical experiment shows a very efficient alignment of the nanorod suspension exhibiting large birefringence under a weak electric field. This result, combined with the high intrinsic transparency and athermal behavior, opens the way towards a new class of self‐assembling materials for electro‐optical applications.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.201200825