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Slow Dynamics and Glass-Like Behavior of Liquid Crystals Dispersed in Nanoporous Media

Published online by Cambridge University Press:  10 February 2011

F. M. Aliev  and
G. P. Sinha
F. M. Aliev
Affiliation:
Department of Physics and Materials Research Center, PO BOX 23343, University of Puerto Rico, San Juan, PR 00931–3343, USA
G. P. Sinha
Affiliation:
Department of Physics and Materials Research Center, PO BOX 23343, University of Puerto Rico, San Juan, PR 00931–3343, USA
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Abstract

We have investigated the dynamic behavior of liquid crystals (LC), which are not glass formers when in bulk form, confined in porous matrices with randomly oriented, interconnected pores as well as in parallel cylindrical pores with different pore sizes by photon correlation (time range: 20 ns-103s) and dielectric spectroscopies (frequencies: 0.1 Hz-1.5GHz). We observed that in random pores (pore size is 10 nm and 100 nm) LC does not crystallize at temperatures about 25° C below bulk crystallization temperature and the non-Debye relaxational processes studied by both photon correlation and dielectric experiments were found not to be frozen. Slow relaxational process which does not exist in bulk LC and a broad spectrum of relaxation times (10−8 − 10)s appear not only for LC in random pores but in cylindrical pores as well. However in matrices with random pores of 100 Å, glass-like behavior of slow mode (τ > 1ms) was observed. The relaxation time (determined in photon correlation experiment) of this slow process strongly increases when temperature decreases from 300 K up to 270 K varying from 0.2ms to 14 s and it's temperature dependence is described by the Vogel-Fulcher law.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 455: Symposium T – Glasses and Glass Formers–Current Issues , 1996 , 273
Copyright
Copyright © Materials Research Society 1997

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