Browsing by Author "Gauza, Sebastian"

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High birefringence lateral difluoro phenyl tolane liquid crystals
(2010)
Song, Qiong
;
Gauza, Sebastian
;
Xianyu, Haiqing
;
Wu, Shin Tson
;
Liao, Yung-Ming
Four laterally difluorinated phenyl tolane liquid crystals were synthesised and their physical properties evaluated. These compounds exhibit a fairly small heat fusion enthalpy (Delta H similar to 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.
High figure-of-merit laterally fluorinated biphenyltolane-isothiocyanates
(2007)
Gauza, Sebastian
;
Zhao, Yang
;
Le Cor, Tatiana
;
Wu, Shin-Tson
;
Ziolek, Anna
We have designed, synthesized, and evaluated the physical properties of some high birefringence (Delta n) isothiocyanato biphenyl-tolane liquid crystals. These compounds exhibit Delta n similar to 0.48-0.52 at room temperature and wavelength lambda = 633 nm. Laterally substituted short alkyl chains and fluorine atom elinlinate smectic phase and lower the melting temperature. The moderate melting temperature and very high clearing temperature make those compounds attractive for eutectic mixture formulation. A eutectic mixture based on those compounds was formulated and its physical properties evaluated.
Synthesis and mesomorphic properties of -methylstilbene-based liquid crystals
(2009)
Chang, Chin-Yen
;
Ho, Kang-Wei
;
Hsu, Chain-Shu
;
Lin, Chih-Hung
;
Gauza, Sebastian
Six series of -methylstilbene-based liquid crystals, i.e. 4-(4-alkylphenyl)-4'-amino--methylstilbenes (2a-e), 4-(4-alkylphenyl)-4'-cyano--methylstilbenes (3a-e), 4-(4-alkylphenyl)-4'-isothiocyanato--methylstilbenes (4a-e), 4'-(trans-4-alkylcyclohexyl)-4-fluoro--methylstilbenes (5a-e), 4'-(trans-4-alkylcyclohexyl)-4-amino--methylstilbenes (7a-e) and 4'-(trans-4-alkylcyclohexyl)-4-isothiocyanato--methylstilbenes (8a-e) were synthesised. All of these -methylstilbene-based compounds exhibit an enantiotropic nematic phase. Some of the 4-(4-alkylphenyl)-4'-isothiocyanato--methylstilbenes with longer alkyl chains exhibit a smectic A phase. All of the liquid crystals obtained exhibit a wide nematic range and high birefringence of 0.16-0.46. Both series of isothiocyanato-based, liquid crystal compounds 4a-e and 8a-e containing -methylstilbenes revealed much lower melting points and clearing temperatures than their cyano and amino homologues.
Synthesis and mesomorphic properties of fluoro and isothiocyanato biphenyl tolane liquid crystals
(2006)
Liao, Yung-Ming
;
Janarthanan, Narayanasamy
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Four series of high birefringence biphenyl tolane liquid crystals having a terminal isothiocyanato or fluoro group were synthesized; their mesomorphic properties were studied by optical polarizing microscopy and DSC. These biphenyl tolane compounds exhibit reasonably low melting points and high birefringence of 0.37-0.49. By using these compounds a eutectic mixture was formulated exhibiting a wide nematic range, high figure-of-merit and low viscosity.
Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals
(2007)
Liao, Yung-Ming
;
Chen, Hsin-Lan
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Four series of high birefringence bistolane liquid crystals containing isothiocyanato termal groups were synthesized and characterized. As well as the phenyl group, both biphenyl and naphthyl moieties were introduced to enhance the birefringence. These bistolane compounds exhibit reasonably low melting points and high birefringence of 0.5-0.8. A eutectic mixture was formulated from these compounds exhibiting a wide nematic range, high figure-of-merit and low viscosity.
Synthesis of laterally substituted alpha-methylstilbene-tolane liquid crystals
(2008)
Chang, Chin-Yen
;
Chien, Szu-Yuan
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Three series of alpha-methylstilbene-tolane liquid crystals, 4-[2-(4-alkylphenyl)-1-ethynyl]-4'-fluoro-alpha-methylstilbene (3a-3e), 4-[2-(4-alkylphenyl)-1-ethynyl]-2'-methyl-4'-fluoro-alpha-methylstilbene (4a-4e) and 4-[2-(4-alkylphenyl)-1-ethynyl]-3'-methyl-4'-fluoro-alpha-methylstilbene (5a-5e), were synthesized and their phase transition temperatures characterized. All the alpha-methylstilbene-tolane liquid crystals exhibit an enantiotropic nematic phase. Compounds 5a-5e, which contain a lateral methyl group at the 3 position of the middle phenyl ring, display low melting points, a wide nematic range and a small enthalpy of fusion. Their potential applications for displays and laser-beam steering are noted.