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Proceedings Paper

Rotational diffusion and orientational fluctuations in polymer-dispersed liquid crystals
Author(s): A. Mertelj; L. Spindler; Martin Copic
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Paper Abstract

Polymer dispersed liquid crystal was studied by dynamic light scattering. In the experiments where no electric field is applied the system exhibits additional slow dynamics to ne observed in bulk nematics. This slow dynamics spreads out over several decades of time and gradually disappears with increasing electric field. It can be attributed to the rotational diffusion of the liquid crystal droplets in random potential as was confirmed by model computations. The random potential is due to the irregularities in the shape of the droplets. While the measured time intensity correlation function does not depend on the scattering vector in the system where no field is applied due to the multiple scattering, its dependence in the electric field shows expected size effects. In confined systems with typical size d there are no eigenmodes of the orientational fluctuations with wave vectors less than minimal wave vector qmin equals (pi) /d. We observed quadratic dependence of the inverse relaxation time on the scattering vector down to certain scattering vector, below which the relaxation time remains constant. The size calculated form this minimal scattering vector is in agreement with the average droplet size obtained from scanning electron microscope photographs and atomic force microscope images of our sample. The electric field changes the temperature behavior of the inverse relaxation time near the nematic-isotropic phase transition which increases with the temperature when electric field is applied, but decreases when the field is absent.

Paper Details

Date Published: 1 February 1998
PDF: 4 pages
Proc. SPIE 3318, Liquid Crystals: Physics, Technology, and Applications, (1 February 1998); doi: 10.1117/12.300018
Show Author Affiliations
A. Mertelj, Jozef Stefan Institute and Univ. of Ljubljana (Slovenia)
L. Spindler, Jozef Stefan Institute and Univ. of Ljubljana (Slovenia)
Martin Copic, Jozef Stefan Institute and Univ. of Ljubljana (Slovenia)

Published in SPIE Proceedings Vol. 3318:
Liquid Crystals: Physics, Technology, and Applications
Jolanta Rutkowska; Stanislaw J. Klosowicz; Jerzy Zielinski; Jozef Zmija, Editor(s)

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