Accession Number : ADP007476

Title :   Dielectric Relaxation Properties and Alignment Behavior of Liquid-Crystalline Side-Chain Polymers,

Corporate Author : UNIVERSITY COLL OF SWANSEA (UNITED KINGDOM) DEPT OF CHEMISTRY

Personal Author(s) : Williams, Graham ; Nazemi, Ali

Report Date : FEB 1991

Pagination or Media Count : 11

Abstract : We describe the alignment behaviour of different liquid crystalline (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.

Descriptors :   *DIELECTRIC PROPERTIES, ALIGNMENT, AMPLITUDE, ANISOTROPY, CHAINS, COPOLYMERS, DIELECTRICS, ELECTRIC FIELDS, FREQUENCY, FUNCTIONS, HISTORY, PARAMETERS, POLYMERS, RELAXATION, SPECTRA, TEMPERATURE, TIME, VARIABLES.

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE