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Optical properties of high-performance liquid crystal–xerogel microcomposite electro-optical film

Published online by Cambridge University Press:  21 March 2012

Martin Timusk ,
Martin Järvekülg ,
Aigi Salundi ,
Rünno Lõhmus ,
Silver Leinberg ,
Ilmar Kink  and
Kristjan Saal
Martin Timusk*
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Martin Järvekülg
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Aigi Salundi
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Rünno Lõhmus
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Silver Leinberg
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Ilmar Kink
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
Kristjan Saal
Affiliation:
Institute of Physics, University of Tartu; and Estonian Nanotechnology Competence Center, Tartu 51014, Estonia
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

Electro-optical films composed of liquid crystal (LC) microdroplets encapsulated in an organically modified xerogel matrix were prepared by combined sol-gel and phase separation methods. The incorporation of a titanium alkoxide in the synthesis process as a co-precursor to silicon alkoxides was achieved without any destructive influence on the macroscopic LC phase separation. The consequent increase in the refractive index of the matrix satisfied the important criteria for high-performance films. The prepared films exhibit an outstanding 75.9% change in transmittance as an electric field is applied. An original setup was developed that enables the measurement of the film transmittance versus applied voltage at different temperatures over the full visible and near-infrared (near-IR) spectral range. For the first time, the relationship between these important characteristics (i.e., change in transmittance versus wave length versus temperature) was measured for a xerogel-dispersed LC composite film. The maximum of the curve increased and moved from the IR to the midvisible range with increasing temperature, achieving its maximum at 25.2 °C and 551 nm.

Keywords

Sol-gelLiquid crystalOptical properties
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 9 , 14 May 2012 , pp. 1257 - 1264
Copyright
Copyright © Materials Research Society 2012

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