Jerzy Dziaduszek

Mesomorphic Characteristics of Some New Homologous Series with the Isothiocyanato Terminal Group

Abstract The synthesis is described and the mesomorphic properties have been tested for two homologous series of compounds with the isothiocyanato (-NCS) terminal group: 4-(trans-4′-n-alkylcyclohexyl)isothiocyanatobenzenes (CHBT—formula 1) and 5-trans-n-alkyl-2-(4′-isothiocyanatophenyl)-1,3-dioxans (DBT—formula 2). CHBT are nematics, and reveal low viscosity and low melting points, DBT are A1 smectics. In this work, binary phase diagrams are presented for mixtures of CHBT or DBT with compounds with the —CN terminal group. CHBT and DBT yield with the latter simple eutectics. Moreover, DBT when mixed with A d smectics at an appropriate smectic layer spacing ratio, yield nematic mixtures. The suitability of CHBT as components of display mixtures is postulated.

Low viscosity, high birefringence liquid crystalline compounds and mixtures

Two types of fast switching mixtures with high positive dielectric anisotropy were described. The first type, with a birefringence below 0.3, was designed for devices operating at room or lower temperatures and the second one, with a birefringence higher than 0.3 for devices operating at elevated temperatures.

Influence of alkoxy chain length and fluorosubstitution on mesogenic and spectral properties of high tilted antiferroelectric esters

The synthesis and properties of a few dozen highly evolved analogues of (S)-MHPOBC are reported. The liquid crystal phases, and phase transition temperatures and enthalpies, as evidenced by polarized optical microscopy and differential scanning calorimetry, respectively, are given. The helical pitch in pure compounds and some mixtures is estimated using the selective reflection method. All of the compounds show antiferroelectric phases, and some key structure–property relationships for the new materials are reported. Specifically, it is found that the length of the oligomethylene segment of a novel partially fluorinated alkoxy ether tail incorporated into the structures strongly influences the stability of the antiferroelectric phase and the observed phase sequences, as well as the values of the helical pitch and its temperature dependence. The formulation of a family of broad temperature range eutectic mixtures possessing the highly desirable orthoconic antiferroelectric phases with long helical pitch is described.

Liquid-CrystalIine 4-(trans-4′-n-AIkyIcyclohexyI) Benzoates. The Effect of Terminal and Lateral Substituents on the Mesomorphic, Thermodynamic and Dielectric Properties

Abstract From 4-(trans-4′-n-akylcyclohexyl)-benzoyl chlorides four series of esters of the general formula: have been prepared. II, n = 5, Z = H, X = H, F, Cl, Br, I, CHO, CH(OCH3)2, COCH3, CN, N(CH3)2, NO2, NCS, SCN, OH, OCOCH3, CH2CN, CH2—CH2CN, alkyl, alkoxyl, phenyl; IIIa and IIIb, n = 2 − 10, Z = H, X = CN(a) and X = NO2(b); IVa and IVb, n = 2 − 10, Z = CN, X = C5H11(a) and X = C4H9(b).

4-/Trans-4′-n-Alkylcyclohezxyl/Isothiocyanatobenzenes a New Class Of Low-Melting Stable Nematics

Abstract The mesogenic properties of four series of compounds with the iso;hiocyanate terminal group are compared, viz.: 4-n-alkyl-4′-isothiocyanatobiphenyls /1/, 4–/trans-4′-n-alkylcyclohexyl/benzeneisothiocyanates /2/, isothiocyanatophenyl 4-n-alkylbenzoates /3 / and isothiocyanatophenyl 4-/trans-4′-n-alkylcyclohexyl/benzoates /4/. It has been found that compounds 2 have only the nematic phase in the homologous series from 2 to 10 carbon atom in the alkyl chain, and compounds 4 the nematic and smectic A phases, while the so far known compounds 1 and 3 are E or A smectics.

Novel high birefringent isothiocyanates based on quaterphenyl and phenylethynyltolane molecular cores

We report the synthesis of new laterally alkyl substituted high birefringent quaterphenyl and phenylethynyltolane liquid crystals with isothiocyanate terminal group. The thermal and optical properties such as birefringence are measured and discussed based on their molecular structures. The compounds exhibit birefringence (Δn) in the range of 0.44–0.63, and are expected to be appropriate components of high birefringent nematic mixtures for various applications.

Synthesis and Mesomorphic Properties of Chiral Esters Comprising Partially Fluorinated Alkoxyalkoxy Terminal Chains and a 1-methylheptyl Chiral Moiety

Two structurally similar homologous series of chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their synthetic routes and mesomorphic properties, such as phase transitions temperatures and enthalpies, are characterized by polarizing optical microscope and differential scanning calorimetry.

Synthesis and Mesomorphic Characteristic of Bicyclo-(2,2,2)Octane Derivatives with the -NCS Terminal Group

Abstract Compounds containing in their molecule an alkyl substituted bicyclo(2,2,2)octane ring and the phenylisothiocyanato group bonded to it directly or via bridging group such as -COO-, -OCO-, -CH2-CH2- or -CH2O- have been synthesized. The phase transition temperatures, melting enthalpies and viscosities of these compounds have been determined and their suitability as components of nematic mixtures has been tested.

New liquid-crystalline isothiocyanates with high clearing points, low viscosities and strong nematic character

Abstract Bi-, tri- and tetra-ring liquid-crystalline compounds with an isothiocyanate group in the terminal position of the molecule and with an ethylene group in the central position have been synthesized. Phenyl, cyclohexyl, bicyclo[2,2,2]octyl, 1,3-dioxane and pyrimidinyl were used as the ring systems. Their transition temperatures and melting enthalpies have been determined. The relationship between the order of the rings in the molecule and the clearing points and melting points of the compounds is discussed. It is shown that these compounds are valuable components of liquid crystal mixtures, since they effectively raise their clearing points yet only have a small effect on the viscosity.

Dielectric properties of ten three-ring LC fluorosubstituted isothiocyanates with different mesogenic cores

Results of the static and dynamic dielectric investigations of 10 liquid crystalline compounds consisting of three rings (phenyl or cyclohexyl) with the n-propyl and isothiocyanato terminals, fluoro lateral substitutes, and different bridging groups (CH2CH2 and/or COO) are presented. These compounds form the nematic phase in a broad temperature range. The dielectric parameters are analyzed in relation to the chemical and dipole structures of the molecules. The influence of different structural elements such as rings, bridging groups and fluorosubstitution on the dielectric properties is discussed. The relaxation time and activation enthalpy characterizing the molecular rotations around the short axes were determined. In the nematic phase, the compounds having two fluorine atoms at the lateral positions exhibit a crossover of the principal permittivity components within the megahertz frequency range. This makes them interesting from the application point of view as the so-called dual frequency materials.