The Fascinating Influence of Fluoro Substituents on the Synthesis and Properties of Liquid Crystals

Hird, Michael; Goodby, John W.; Lewis, Robert A.; Toyne, Kenneth J.

doi:10.1080/744814910

Cited by 30 publications

(11 citation statements)

References 32 publications

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“…35,39 Compound 2 (C 9 F) exhibits the largest absolute value of D3 varying from À2.8 (T À T NI ¼ À3.4 K) to À4.4 (T À T NI ¼ À14.4 K) and the effect can be attributed to the conjugative mesomeric effect of the phenyl ether oxygen on the lateral uoro substituents, as is seen for calamitic NLCs. 40 Compound 4, which has one terminal alkyl chain replacing the alkoxy chain, has the smallest dielectric anisotropy, varying from just À1.4 (T À T NI ¼ À8.7 K) to À3.2 (T À T NI ¼ À56.7 K); this is approximately half of the value measured in compounds 1-3. While such a variation could be due to the different terminal chain in compound 4, it is to be remembered that the alkyl chain is only C 5 , i.e., it is somewhat shorter than in the other materials.…”

Section: Dielectric Anisotropy and Elastic Constantsmentioning

confidence: 96%

The influence of structure on the elastic, optical and dielectric properties of nematic phases formed from bent-core molecules

et al. 2013

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The physical properties of the nematic phases formed by four bent-core oxadiazole based materials are reported. In particular, the splay (K11), twist (K22) and bend (K33) elastic constants, the birefringence and the dielectric anisotropy of the materials are described and the effect of chain length and the presence of fluoro-substituents at the outer phenylene group of the aromatic core structure on these parameters is determined. The birefringence and order parameter are found to be independent of the modification of molecular structure. The dielectric anisotropy is quite strongly dependent on molecular structure; the fluoro-substituted material has the largest magnitude of dielectric anisotropy while the alkyl-substituted compound has the smallest. Changes in the molecular length and fluoro-substitution in the bent-core materials are found to have little influence on the splay, twist and bend elastic constants at equivalent reduced temperatures. However, the material substituted with an alkyl terminal chain exhibits both smaller elastic constants and a less marked dependence on temperature than the alkoxy-substituted compounds. A possible insight into the behaviour of the elastic constants relevant to the formation of the dark conglomerate phase, which underlies the nematic phase in one of the compounds studied, is suggested by following the analysis proposed by Berreman and Meiboom. Importantly, using molecular field theory and atomistic modelling, we calculate elastic constants that are in excellent agreement with the experimental values. Our conclusion that the elasticity in the nematic phase formed from bent-core molecules is not strongly influenced by changes to the terminal chains or the presence of fluoro- substituents at the outer phenylene group of the aromatic core structure is in agreement with our previous work showing that the dominant parameter is the bend angle

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Section: Dielectric Anisotropy and Elastic Constantsmentioning

confidence: 96%

The influence of structure on the elastic, optical and dielectric properties of nematic phases formed from bent-core molecules

et al. 2013

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“…Fluorinated calamitic thermotropic liquid crystals (F‐LCs) represent an important class of materials with optimized properties for advanced high technology applications in electro‐optical devices, such as active matrix liquid crystal displays (AM‐LCDs), twisted nematic and super twisted nematic liquid crystal displays (TN‐LCDs and STN‐LCDs, respectively), and surface stabilized ferroelectric displays (SSF‐LCDs) . Fluoro substituents, characterized by both small size and high polarity, can be usefully located at many different sites (e.g.…”

Section: Introductionmentioning

confidence: 99%

Orientational ordering studies of fluorinated thermotropic liquid crystals by NMR spectroscopy

Calucci

Geppi

Urban

2014

Magnetic Reson in Chemistry

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Fluorinated calamitic thermotropic liquid crystals represent an important class of materials for high-tech applications, especially in the field of liquid crystal displays. The investigation of orientational ordering in these systems is fundamental owing to the dependence of their applications on the anisotropic nature of macroscopic optical, dielectric, and visco-elastic properties. NMR spectroscopy is the most powerful technique for studying orientational order in liquid crystalline systems at a molecular level thanks to the possibility of exploiting different anisotropic observables (chemical shift, dipolar couplings, and quadrupolar coupling) and nuclei ((2)H, (13)C, and (19)F). In this paper, the basic theory and NMR experiments useful for the investigation of orientational order on fluorinated calamitic liquid crystals are reported, and a review of the literature published on this subject is given. Finally, orientational order parameters determined by NMR data are discussed in comparison to those obtained by optical and dielectric anisotropy measurements.

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“…Early in the 1980s Ken Toyne was examining ways to make monofluorinated terphenyls (21), and it had occurred to him that if one lateral fluorine substituent in terphenyl could induce beneficial mesomorphic and physical properties for ferroelectric liquid crystals, then maybe two substituents might improve those properties further. Using the Nobel prizewinning Suzuki-Miyaura boronic acid coupling technique, difluoroterphenyls were prepared by Toyne's student, Hird, as host materials for ferroelectric liquid crystals ( 22) (Hird et al 2003). At a similar time it was realized, for nematic homologues, that it would be possible to use the materials for electrically controlled birefringence devices in which the molecules in the 'off-state or dark-state' are aligned vertically with respect to the glass substrates.…”

Section: A Scientific Revolutionmentioning

confidence: 99%

George William Gray CBE MRIA FRSE. 4 September 1926 — 12 May 2013

Goodby

Raynes

2016

Biogr. Mems Fell. R. Soc.

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George Gray was a renowned British materials chemist, internationally distinguished for his research into liquid crystals and their applications in flat-panel displays. His seminal invention of the liquid-crystalline cyanobiphenyls underpinned the creation of the modern electronic displays industry, which began with digital watches and has continued through to smart and three-dimensional televisions. There are now more liquid crystal displays in the world than people, and these devices have engendered societal changes through social networking on the Internet. His ability to design, synthesize and utilize self-organizing materials across the various disciplines of science showed that he was a supreme molecular engineer. For his contributions to soft-matter and related advanced technologies he was made a Commander of the British Empire, Kyoto Prize laureate, Fellow of the Royal Society, Fellow of the Royal Society of Edinburgh and Honorary Member of the Royal Irish Academy. Early years and familyGeorge Gray was born to John and Jessie Gray in Denny, Scotland, on 4 September 1926. He was an ordinary, happy and mischievous boy brought up in a stable and loving family. He was the only son, but he did have a sister, Catherine, six years his senior. As a child his main interests were making models of ships, reading, and growing plants and gardening. The small town of Denny, where he grew up, was not particularly attractive because it was centred on coal mining, paper manufacture and iron production. However, as it had easy access to the surrounding and beautiful countryside, his memories were of hills and rivers, not industrial grime.George's mother was much closer to his sister than she was to George; maybe she found him too lively, untidy and mischievous-for example, he once tied his nanny to a chair. In

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The Fascinating Influence of Fluoro Substituents on the Synthesis and Properties of Liquid Crystals

Cited by 30 publications

References 32 publications

The influence of structure on the elastic, optical and dielectric properties of nematic phases formed from bent-core molecules

The influence of structure on the elastic, optical and dielectric properties of nematic phases formed from bent-core molecules

Orientational ordering studies of fluorinated thermotropic liquid crystals by NMR spectroscopy

George William Gray CBE MRIA FRSE. 4 September 1926 — 12 May 2013

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