The electro-optic properties of liquid crystalline materials for optical device applications
The electro-optic properties of liquid crystalline materials for optical device applications
In the present work two series of low molar mass organosiloxane liquid crystals, which combine the high tilt and wide phase range properties of laterally substituted biphenyl benzoate mesogens with the polymer ruggedness of siloxane head groups, were investigated. The mono-mesogens exhibit a 50≡C wide ferroelectric SmC* phase and a Ps of ~100nC/cm2. Temperature independent, near 45≡ or 45≡ tilt angles were measured for all three compounds. Response time measurements revealed that switching as fast as 30μs was achievable. It was found that the phase behaviour of the bi-mesogenic compounds was strongly influenced by the length of the siloxane group. The tri-siloxane and penta-siloxane bi-mesogenic compounds were antiferroelectric over 70≡C wide ranges, whilst Cl11-4-11Cl displayed ferroelectric behaviour. The spontaneous polarisation was enhanced to 100-140 nCcm-2 whilst the other electro-optic properties had similar magnitudes and broadly followed similar trends to the mono-siloxane compounds.
A series of mixtures, of achiral nematic bimesogens and small concentrations of chiral dopants, designed to exhibit enhanced flexoelectric switching were studied. All the mixtures exhibited a single chiral nematic phase on cooling from the isotropic phase. The uniformly lying helix texture, necessary to observe flexoelectric switching was achieved through a combination of turbulent flow induced by an applied electric field and suitably treated surfaces. Exceptional room temperature tilt angles of 45≡ and switching times of the order of 500μs were measured.
A series of mixtures, of a proprietary dual frequency nematic compound and a low viscosity host were characterised. The temperature dependent behaviour of the crossover frequency was characterised, along with the frequency dependence of Δε and VTH. Response times of ~5ms were achieved for an applied field of ±2V/μm. Dual frequency addressing was shown to be advantageous at temperatures far below TNI, with response times decreasing by a factor of two.
University of Southampton
Noot, Christopher David John
5615b6f0-ab85-40b6-9742-f2d9af717ff6
2003
Noot, Christopher David John
5615b6f0-ab85-40b6-9742-f2d9af717ff6
Noot, Christopher David John
(2003)
The electro-optic properties of liquid crystalline materials for optical device applications.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In the present work two series of low molar mass organosiloxane liquid crystals, which combine the high tilt and wide phase range properties of laterally substituted biphenyl benzoate mesogens with the polymer ruggedness of siloxane head groups, were investigated. The mono-mesogens exhibit a 50≡C wide ferroelectric SmC* phase and a Ps of ~100nC/cm2. Temperature independent, near 45≡ or 45≡ tilt angles were measured for all three compounds. Response time measurements revealed that switching as fast as 30μs was achievable. It was found that the phase behaviour of the bi-mesogenic compounds was strongly influenced by the length of the siloxane group. The tri-siloxane and penta-siloxane bi-mesogenic compounds were antiferroelectric over 70≡C wide ranges, whilst Cl11-4-11Cl displayed ferroelectric behaviour. The spontaneous polarisation was enhanced to 100-140 nCcm-2 whilst the other electro-optic properties had similar magnitudes and broadly followed similar trends to the mono-siloxane compounds.
A series of mixtures, of achiral nematic bimesogens and small concentrations of chiral dopants, designed to exhibit enhanced flexoelectric switching were studied. All the mixtures exhibited a single chiral nematic phase on cooling from the isotropic phase. The uniformly lying helix texture, necessary to observe flexoelectric switching was achieved through a combination of turbulent flow induced by an applied electric field and suitably treated surfaces. Exceptional room temperature tilt angles of 45≡ and switching times of the order of 500μs were measured.
A series of mixtures, of a proprietary dual frequency nematic compound and a low viscosity host were characterised. The temperature dependent behaviour of the crossover frequency was characterised, along with the frequency dependence of Δε and VTH. Response times of ~5ms were achieved for an applied field of ±2V/μm. Dual frequency addressing was shown to be advantageous at temperatures far below TNI, with response times decreasing by a factor of two.
Text
971250.pdf
- Version of Record
More information
Published date: 2003
Identifiers
Local EPrints ID: 465539
URI: http://eprints.soton.ac.uk/id/eprint/465539
PURE UUID: 98a3cdf2-d660-4217-9f6c-af9124befbec
Catalogue record
Date deposited: 05 Jul 2022 01:40
Last modified: 16 Mar 2024 20:14
Export record
Contributors
Author:
Christopher David John Noot
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics