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Dielectric Relaxation Properties and Alignment Behaviour of Liquid-Crystalline Side-Chain Polymers

Published online by Cambridge University Press:  21 February 2011

Graham Williams ,
Ali Nazemi  and
Frank E Karasz
Graham Williams
Affiliation:
University College of Swansea, Department of Chemistry, Singleton Park, Swansea SA2 8PP, United Kingdom
Ali Nazemi
Affiliation:
University College of Swansea, Department of Chemistry, Singleton Park, Swansea SA2 8PP, United Kingdom
Frank E Karasz
Affiliation:
University of Massachusetts, Department of Polymer Science and Engineering, Amherst, MA01003, USA.
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Abstract

We describe the alignment behaviour of different liquidcrystalline (LC) side-chain polymers when they are subjected to electrical/thermal treatments. It is shown that the alignment behaviour is determined by several variables for a given polymer, including the amplitude and frequency of the applied electric field and both the thermal and electrical history of the sample and its low-field dielectric relaxation properties. It is shown that the dielectric relaxation spectra vary systematically with the degree of macroscopic alignment of the sample and its temperature. The anisotropy of dielectric properties may be understood in terms of the anisotropic reorientational motions of the dipolar mesogenic groups. The permittivity data allow the degree of macroscopic alignment to be determined, via a director order parameter Sd for samples prepared in different ways and also for samples being realigned, as a function of time, by directing electric fields. We illustrate these principles through data we have obtained for a copolymer having the mesogenic groups attached longitudinally and transversely to the main chain.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 175: Symposium S – Multifunctional Materials , 1989 , 227
Copyright
Copyright © Materials Research Society 1990

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