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| Articles
by
Sebastian Gauza |
Total Records (
5 ) for
Sebastian Gauza |
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Sebastian Gauza
,
Amanda Parish
,
Shin-Tson Wu
,
Anna Spadlo
and
Roman Dabrowski
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We have designed, synthesised and evaluated the physical properties of high-birefringence (Δn) isothiocyanato phenyl-tolane and terphenyl liquid crystals. These compounds exhibit a Δn∼0.36-0.52 at room temperature and wavelength λ = 633 nm. A different mesomorphic sequence was observed depending on the terminal alkyl chain length. Compounds with a longer chain show smectic and nematic phases, whereas short-chain homologues only exhibit a nematic phase. In the vicinity of the nematic-to-smectic transition, the viscoelastic coefficient decreases, instead of increases, as the temperature decreases. The observed change is as large as 75% for the 4`-(3,5-difluoro-4-isothiocyanatophenylethynyl)-4-pentylbiphenyl compound studied. This behaviour is useful for improving the response time of a liquid crystal device, if the operating temperature can be controlled accurately. |
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Haiqing Xianyu
,
Yue Zhao
,
Sebastian Gauza
,
Xiao Liang
and
Shin-Tson Wu
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Some high birefringence ester liquid crystal compounds with cyanate or isothiocyanate polar groups were investigated, the relaxation frequency of which is in the kilo-Hertz region. These compounds are useful for formulating dual-frequency liquid crystal (DFLC) mixtures. The dielectric relaxation and electro-optical properties of these compounds were characterised. Potential applications of these compounds for DFLC mixtures to meet different requirements are discussed. |
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Qiong Song
,
Sebastian Gauza
,
Jie Sun
,
Shin Tson Wu
and
Xiao Liang
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Lateral difluoro terphenyls exhibit a high birefringence, fairly low viscosity and modest dielectric anisotropy, but their alignment in a vertical alignment (VA) cell often deteriorates at elevated temperatures if their concentration is high. We have studied the effects of six diluters for lowering the viscosity while stabilizing the VA of the terphenyl host mixture at elevated temperatures. The pros and cons of each diluter are analysed. |
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Qiong Song
,
Sebastian Gauza
,
Haiqing Xianyu
,
Shin Tson Wu
,
Yung-Ming Liao
,
Chin-Yen Chang
and
Chain-Shu Hsu
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Four laterally difluorinated phenyl tolane liquid crystals were synthesised and their physical properties evaluated. These compounds exhibit a fairly small heat fusion enthalpy (ΔH ∼ 12.56 kJ mol-1), which is favourable for mixture formulations. For comparison, four lateral difluoro cyclohexane tolane homologues are also studied. We doped 10 wt% of each compound into a commercial negative mixture N1 and measured the birefringence, visco-elastic coefficient and figure of merit. Birefringence varies very little between homologues, but the visco-elastic coefficient increases as alkyl chain length increases. The refractive indices of these guest-host mixtures at 1550 nm are also measured. |
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Sukin Yoon
,
Miyoung Kim
,
Min Su Kim
,
Byeong Gyun Kang
,
Mi-Kyung Kim
,
Anoop Kumar Srivastava
,
Seung Hee Lee
,
Zhibing Ge
,
Linghui Rao
,
Sebastian Gauza
and
Shin-Tson Wu
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Liquid crystal displays based on the Kerr effect are emerging because of their attractive features, such as symmetric viewing angle, no need for alignment layer, and sub-millisecond response time. However, high operating voltage and low optical efficiency remain as challenges to be overcome. Here, we propose a new cell structure with a protrusion shape of electrode and a driving scheme using two transistors to reduce operating voltage and enhance light efficiency. Confirming simulation results are obtained. |
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