High Birefringence Nematic Liquid Crystals for Display and Telecom Applications

Catanescu, Carmen Otilia; Chien, Liang–Chy; Wu, Shin‐Tson

doi:10.1080/15421400490434829

Cited by 20 publications

(9 citation statements)

References 5 publications

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“…The isothiocyanates as compounds with the high Dn seem to be more suitable than other polar ones because of lower viscosity. Many isothiocyanato (NCS) compounds have been prepared and described recently [4][5][6][7] but mainly alkoxy derivatives were presented.…”

Section: Introductionmentioning

confidence: 99%

Low viscosity, high birefringence liquid crystalline compounds and mixtures

Dąbrowski¹,

Dziaduszek

Ziółek

et al. 2007

Opto-Electronics Review

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Section: Introductionmentioning

confidence: 99%

Low viscosity, high birefringence liquid crystalline compounds and mixtures

Dąbrowski¹,

Dziaduszek

Ziółek

et al. 2007

Opto-Electronics Review

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“…A white crystal of 28 g was obtained with yield of 88%. 1 1a-1e, 2a-2e, 3a-3e were prepared by the same procedure described in the preparation of 2b.…”

Section: Synthesis Of 1-bromo-2-fluoro-4-((4-propylphenyl) Ethynyl)bementioning

confidence: 99%

“…High birefringence liquid crystal materials have important applications not only in the field of display but also in telecom, [1] microwave [2] and terahertz fields. [3,4] In order to obtain compounds with high birefringence, the most effective method is to extend the molecular conjugation chain length.…”

Section: Introductionmentioning

confidence: 99%

The effect of lateral fluorination on the properties of phenyl-tolane liquid crystals

Li¹,

Yang²,

Gan³

et al. 2015

Liquid Crystals

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Multifluorinated phenyl-tolane liquid crystals were synthesised by two steps cross-coupling reactions, and their structures were confirmed by nuclear magnetic resonance (NMR), mass spectra (MS) and infrared spectrometry (IR). All of these compounds show only nematic phase, and their melting points decrease dramatically with the introduction of lateral fluorine atom. The physical properties of the compounds were also evaluated. The extrapolated birefringence of the compounds are at the range of 0.32-0.37 at 589 nm, and the dielectric anisotropies exist between 3.1 and 20.6, and the rotational viscosities are as low as 63.7-130.7 mPa·s. With the increase of lateral fluorine substituents in the benzene ring, the Δε value increases tremendously while the clearing points, birefringence and rotational viscosity decrease. These compounds show good solubilities and are favourable to form eutectic mixtures. The effect of lateral fluorine atoms at different region of the core on the dielectric anisotropy and mesophase is also discussed.

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“…The laterally fluorinated liquid crystal compounds have attracted recent attention because of their potential applications in display technology and telecommunications. [1][2][3][4][5][6][7][8][9] The replacement of hydrogen with the fluorine on the aromatic core reduces the melting point and smectogenity leading to a wide nematic range. Mixtures of these singly or doubly fluorinated compounds on the aromatic cores have high figureof-merit, low viscosity, and high birefringence, which are the favorable physical parameters for liquid crystal display devices.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed dielectric studies were carried out on singly fluorinated compounds to examine the correlation times of reorientations. 6 Our present interest is to examine possible differences in the relaxation mechanisms of 1 H and 19 F residing on the molecule of a singly fluorinated liquid crystal (both nuclei being spin- 1 2 , with comparable gyromagneteic ratios differing by about 6%) using NMR relaxometry. This has the potential to yield perhaps different perspectives of dynamic processes of the same molecule as reported by the two distinct probing nuclei.…”

Section: Introductionmentioning

confidence: 99%

Slow dynamics in a liquid crystal: 1H and 19F NMR relaxometry

Rajeswari

Molugu

Dhara

et al. 2011

The Journal of Chemical Physics

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Spin-lattice relaxation rates (R(1H) and R(1F)) of two nuclear species ((1)H and (19)F) are measured at different temperatures in the isotropic phase of a liquid crystal (4(')-butoxy-3(')-fluoro-4-isothiocyanatotolane-4OFTOL), over a wide range of Larmor frequency (10 kHz-50 MHz). Their dispersion profiles are found to be qualitatively very different, and the R(1F) in particular shows significant dispersion (varying over two orders of magnitude) in the entire isotropic range, unlike R(1H). The proton spin-lattice relaxation, as has been established, is mediated by time modulation of magnetic dipolar interactions with other protons (case of like spins), and the discernable dispersion in the mid-frequency range, observed as the isotropic to nematic transition is approached on cooling, is indicative of the critical slowing of the time fluctuations of the nematic order. Significant dispersion seen in the R(1F) extending to very low frequencies suggests a distinctly different relaxation path which is exclusively sensitive to the ultra slow modes apparently present in the system. We find that under the conditions of our experiment at low Zeeman fields, spin-rotation coupling of the fluorine with the molecular angular momentum is the dominant mechanism, and the observed dispersion is thus attributed to the presence of slow torques experienced by the molecules, arising clearly from collective modes. Following the arguments advanced to explain similar slow processes inferred from earlier detailed ESR measurements in liquid crystals, we propose that slowly relaxing local structures representing such dynamic processes could be the likely underlying mechanism providing the necessary slow molecular angular momentum correlations to manifest as the observed low frequency dispersion. We also find that the effects of the onset of cross-relaxation between the two nuclear species when their resonance lines start overlapping at very low Larmor frequencies (below ~400 kHz), provide an additional relaxation contribution.

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High Birefringence Nematic Liquid Crystals for Display and Telecom Applications

Cited by 20 publications

References 5 publications

Low viscosity, high birefringence liquid crystalline compounds and mixtures

Low viscosity, high birefringence liquid crystalline compounds and mixtures

The effect of lateral fluorination on the properties of phenyl-tolane liquid crystals

Slow dynamics in a liquid crystal: 1H and 19F NMR relaxometry

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