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Deuterium NMR investigation of field-induced director dynamics: the role of backflow

Deuterium NMR investigation of field-induced director dynamics: the role of backflow
Deuterium NMR investigation of field-induced director dynamics: the role of backflow
Deuterium NMR spectroscopy has been used to investigate the director dynamics in the nematic liquid crystal, 4-pentyl-4 ' -cyanobiphenyl, confined between two glass plates and subject to orthogonal magnetic and pulsed electric fields. When the pulsed electric field, whose intensity is strong enough to make the director align normal to the magnetic field, is applied to the nematic film, the director moves from being parallel to the magnetic field to being parallel to the electric field. After the pulsed electric field is switched off, the director relaxes back to being parallel to the magnetic field. Deuterium NMR spectra were recorded during the turn-off realignment process as a function of time. With this experimental geometry the director alignment is not unique as it can rotate equally probably clockwise or counterclockwise in this realignment process. That is, the realignment pathway for the director is degenerate, which establishes a director flow pattern. We have studied the time dependence of the director orientation and distribution for the turn-off process. The deuterium NMR spectra corresponding to the director dynamics in the realignment pathways were predicted by a continuum theory analysis including a time dependent viscous torque with an effective rotational viscosity.
nmr, director dynamics, liquid crystal nematic liquid-crystal, orientational order, polymer, reorientation, phase
0040-6090
399-406
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Miyamoto, Tetsuo
82904196-6d2d-413a-b9e5-95a5d4bc8171
Sugimura, Akihiko
d252f7e8-4859-414d-9f81-db4ec4985b03
Timimi, Bakir A.
845f8bba-a04b-4e8d-adfe-51b13e9f29ca
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Miyamoto, Tetsuo
82904196-6d2d-413a-b9e5-95a5d4bc8171
Sugimura, Akihiko
d252f7e8-4859-414d-9f81-db4ec4985b03
Timimi, Bakir A.
845f8bba-a04b-4e8d-adfe-51b13e9f29ca

Luckhurst, Geoffrey R., Miyamoto, Tetsuo, Sugimura, Akihiko and Timimi, Bakir A. (2001) Deuterium NMR investigation of field-induced director dynamics: the role of backflow. Thin Solid Films, 393 (1-2), 399-406. (doi:10.1016/S0040-6090(01)01127-0).

Record type: Article

Abstract

Deuterium NMR spectroscopy has been used to investigate the director dynamics in the nematic liquid crystal, 4-pentyl-4 ' -cyanobiphenyl, confined between two glass plates and subject to orthogonal magnetic and pulsed electric fields. When the pulsed electric field, whose intensity is strong enough to make the director align normal to the magnetic field, is applied to the nematic film, the director moves from being parallel to the magnetic field to being parallel to the electric field. After the pulsed electric field is switched off, the director relaxes back to being parallel to the magnetic field. Deuterium NMR spectra were recorded during the turn-off realignment process as a function of time. With this experimental geometry the director alignment is not unique as it can rotate equally probably clockwise or counterclockwise in this realignment process. That is, the realignment pathway for the director is degenerate, which establishes a director flow pattern. We have studied the time dependence of the director orientation and distribution for the turn-off process. The deuterium NMR spectra corresponding to the director dynamics in the realignment pathways were predicted by a continuum theory analysis including a time dependent viscous torque with an effective rotational viscosity.

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More information

Published date: 1 August 2001
Keywords: nmr, director dynamics, liquid crystal nematic liquid-crystal, orientational order, polymer, reorientation, phase

Identifiers

Local EPrints ID: 19566
URI: http://eprints.soton.ac.uk/id/eprint/19566
ISSN: 0040-6090
PURE UUID: bb24eb34-4960-4b69-9b25-718bcd02f910

Catalogue record

Date deposited: 15 Feb 2006
Last modified: 15 Jul 2019 19:27

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