Photoisomerising effects in chrial liquid crystal systems
Photoisomerising effects in chrial liquid crystal systems
Photoisomerising liquid crystals are added to smectic and chiral nematic systems. The consequences of dye addition to the phase sequence and switching properties of the host material are described. The effect of ultra violet illumination, causing a shape changing photoisomerisation of the dye molecules, on these mixtures is explored.
The photoisomerisation of the azobenzene molecules, used as dyes, is to change the straight trans isomer that is very compatible with the liquid crystalline phase to the bent cis isomer that is less compatible. This conversion is caused by illumination by ultra violet, the reverse isomerisation can be caused thermally or by illumination by infra red wavelengths.
Organosiloxane liquid crystals produce stable ferroelectric semectic C* liquid crystalline phases that have a tilt angle close to 45o and a high spontaneous polarisation. The effect of monomesogenic and bimesogenic dye addition was to add a smectic A phase to the sequence, which showed a large electroclinic, effect and aided the alignment of the ferroelectric phase. The bimesogenic dye acted as a template for the monomesogenic host molecules, inducing an anticlinic antiferroelectric arrangement.
The effect of ultra violet illumination was to reversibly reduce the phase transition temperatures, the spontaneous polarisation and the tilt angle of the mixtures indicating a reduction in the order of the system.
Azobenzene dyes were added to chiral nematic bimesogens mixtures with a high flexoelectric coefficient. The effect of ultra violet was to reduce the phase transition temperatures and the helical pitch. The response time and tilt angle were unchanged. The results indicate a reduction in the order parameter but no measurable change of the flexoelectric constants.
University of Southampton
Remnant, Anna Marie
b97d2754-7e65-4f1e-8c44-6c7b8d73fd35
2002
Remnant, Anna Marie
b97d2754-7e65-4f1e-8c44-6c7b8d73fd35
Remnant, Anna Marie
(2002)
Photoisomerising effects in chrial liquid crystal systems.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Photoisomerising liquid crystals are added to smectic and chiral nematic systems. The consequences of dye addition to the phase sequence and switching properties of the host material are described. The effect of ultra violet illumination, causing a shape changing photoisomerisation of the dye molecules, on these mixtures is explored.
The photoisomerisation of the azobenzene molecules, used as dyes, is to change the straight trans isomer that is very compatible with the liquid crystalline phase to the bent cis isomer that is less compatible. This conversion is caused by illumination by ultra violet, the reverse isomerisation can be caused thermally or by illumination by infra red wavelengths.
Organosiloxane liquid crystals produce stable ferroelectric semectic C* liquid crystalline phases that have a tilt angle close to 45o and a high spontaneous polarisation. The effect of monomesogenic and bimesogenic dye addition was to add a smectic A phase to the sequence, which showed a large electroclinic, effect and aided the alignment of the ferroelectric phase. The bimesogenic dye acted as a template for the monomesogenic host molecules, inducing an anticlinic antiferroelectric arrangement.
The effect of ultra violet illumination was to reversibly reduce the phase transition temperatures, the spontaneous polarisation and the tilt angle of the mixtures indicating a reduction in the order of the system.
Azobenzene dyes were added to chiral nematic bimesogens mixtures with a high flexoelectric coefficient. The effect of ultra violet was to reduce the phase transition temperatures and the helical pitch. The response time and tilt angle were unchanged. The results indicate a reduction in the order parameter but no measurable change of the flexoelectric constants.
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Published date: 2002
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Local EPrints ID: 465003
URI: http://eprints.soton.ac.uk/id/eprint/465003
PURE UUID: 07e8ee2f-01df-435e-927a-3e89cae22146
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Date deposited: 05 Jul 2022 00:15
Last modified: 16 Mar 2024 19:53
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Author:
Anna Marie Remnant
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