The invention relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy (Δe), which contains at least one compound selected from the group of compounds of the formula I, II A and II B and at least one compound of the formula I* in which R0, R1, R2, R1*, X1, X2, A1, A1*, A2*, Z1, Z1*, Z2*, L1*, L2*, p, q, v, m and m* are as defined in Claim 1, and to the use thereof for an active-matrix display based on the ECB, VA, PS-VA, FFS, PALC or IPS effect.

Liquid Crystalline Medium

This critical review begins with a brief, but essential, introduction to the special nature of liquid crystal materials, their peculiar properties, and their commercial applications, followed by an introductory insight into the remarkable nature of the fluoro substituent, and its fascinating influence on the properties of organic compounds. However, the main focus of the review is to discuss the enormous amount of exciting research on fluorinated liquid crystals that has been reported. The small size of the fluoro substituent enables its incorporation into all types of liquid crystal, including calamitic, discotic, banana, lyotropic, and polymers, without ruining the liquid crystalline nature of the material. However the fluoro substituent is larger than hydrogen, and hence causes a significant steric effect, which combined with the high polarity, confers many fascinating, and often remarkable, modifications to melting point, mesophase morphology and transition temperatures, and the many other very important physical properties, such as dielectric anisotropy, optical anisotropy, and visco-elastic properties. There are many different positions within a liquid crystal structure where a fluoro substituent can be located, including (i) a terminal position, (ii) within a terminal chain, as a semi-fluorinated or as a perfluorinated chain, or as one fluoro substituent at a chiral centre, (iii) as part of a linking group, and (iv) a lateral position in the core section. Such variety enables the interesting and advantageous tailoring of properties, both for the fundamental purposes of establishing structure–property relationships, and for materials targeted towards commercially-successful liquid crystal display applications.

Fluorinated liquid crystals – properties and applications

Substances forming calamitic mesophases have been known for more than 100 years but only the recent, rapid advance in active matrix liquid crystal display (AM-LCD) technology helped these materials to achieve the crucial position in flat panel display technology they hold today. Due to their high contrast, large viewing angle, and rapid switching times, modern AM-LCDs offer a superior picture quality even compared to conventional cathode ray tubes. Their flatness, low weight, and low energy consumption render them the technology of choice for all kinds of portable devices. Some of the future promises of AM-LCD technology are centered around the development of liquid crystalline materials for the different subtypes of active matrix applications. This development is aimed, on the one hand, towards improved electrooptical and viscoelastic properties; on the other hand, the increasing performance of LCDs leads to extremely stringent reliability demands on the liquid crystals. Responding to these high standards of performance and quality, most liquid crystals for contemporary AM-LCD applications are multiply fluorinated compounds with very high purities, as is typical for materials used in the electronics industry. The synthesis of these superfluorinated materials (SFMs) often requires specialized methods, which, in several cases, had to be introduced for the first time into the canon of industrial production. The immense market pressure, as well as the rapid advance of AM-LCD technology on the side of the display manufacturers, urges an increasing pace of the materials development. This demand for new materials can no longer be fulfilled by conventional trial-and-error approaches. As in the pharmaceutical industry, in the search for new, superior liquid crystals, the purely empirical methods are increasingly supported by a rational design based on computational methods.

Nematic Liquid Crystals for Active Matrix Displays: Molecular Design and Synthesis.

Induction of smectic layering in nematic liquid crystals using immiscible components. 1. laterally attached side-chain liquid crystalline poly(norborn ene)s and their low molar mass analogs with hydrocarbon/fluorocarbon substi tuents

A main group-catalyzed method for the synthesis of aryl- and heteroarylamines by intermolecular C–N coupling is reported. The method employs a small-ring organophosphorus-based catalyst (1,2,2,3,4,4-hexamethylphosphetane) and a terminal hydrosilane reductant (phenylsilane) to drive reductive intermolecular coupling of nitro(hetero)arenes with boronic acids. Applications to the construction of both Csp2–N (from arylboronic acids) and Csp3–N bonds (from alkylboronic acids) are demonstrated; the reaction is stereospecific with respect to Csp3–N bond formation. The method constitutes a new route from readily available building blocks to valuable nitrogen-containing products with complementarity in both scope and chemoselectivity to existing catalytic C–N coupling methods.

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Intermolecular Reductive C–N Cross Coupling of Nitroarenes and Boronic Acids by PIII/PV═O Catalysis

The paper reports synthesis of LC derivatives of different chemical classes containing terminal groups ‒OCHF2, ‒OCF3, ‒SCHF2, ‒OCnF2n +1 and ‒CnF2n + 1 and indicates their phase transition points and physico-chemical properties.

Synthesis and Properties of Liquid Crystals with Fluorinated Terminal Substituents

Polymorphism and intermolecular interactions in crystalline fluorinated alkylbenzoic acids

Several new classes of low polar, low viscous and optically weak anisotropic two- and three-ring halogenated liquid crystals containing terminal group -OCF2Cl are presented. Their material properties are investigated and compared with those of other halogenated liquid crystals.

Synthesis and Properties of new Halogenated Liquid Crystals

For the first time the MBBA analogues comprising of perfluorinated methoxy- and/or n-butyl groups have been synthesized and their mesomorphic properties have been studied. It has been shown that introduction of fluorine atoms into at least one of the substituents causes the appearance of a smectic mesophase, and that the compound comprised of both CF3O and n-C4F9- groups possesses no mesomorphic properties.

Fluorinated Analogues of Liquid Crystals 1. Analogues of 4-Methoxybenzylidene-4'-Butylaniline with Perfluorinated Alkyl- and Alkoxy-Groups

The inflammatory process is, as known, a pathological symptom of many illnesses. Therefore, the regulation of the inflammatory reaction, including that by means of pharmacological compounds, is one of the important problems of modern medicine. In particular, medicinal compounds are used in clinics, which inhibit the development of the inflammatory process. The suppression of inflammation makes it possible to shorten the time of the illness and to decrease the gravity of the disease and its consequences.

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Yu. A. Fialkov

Papers

Synthesis and Properties of Liquid Crystals with Fluorinated Terminal Substituents

Polymorphism and intermolecular interactions in crystalline fluorinated alkylbenzoic acids

Synthesis and Properties of new Halogenated Liquid Crystals

Fluorinated Analogues of Liquid Crystals 1. Analogues of 4-Methoxybenzylidene-4'-Butylaniline with Perfluorinated Alkyl- and Alkoxy-Groups

Mefenamic acid — A nonsteroid antiinflammatory agent