Vladimir F. Petrov

The oxadiazole as a structural fragment in liquid crystals

This paper examines in some detail the effect of introducing the oxadiazole fragment into the molecular core of liquid crystals on their physico-chemical properties. The results of this study are compared with those obtained for other molecular fragments, and are rationalized in terms of existing theories.

Liquid crystal pyridine derivatives of high positive dielectric anisotropy

Abstract Pyridine derivatives of general formula I-YII have been synthesized. Phase transition temperatures and physico-chemical properties of the compounds are given.

Nitrogen-containing fused heterocycles as the structural fragments in calamitic liquid crystals

This review examines in some detail the effect of introducing nitrogen-containing fused heterocycles into the molecular core of calamitic liquid crystals on their physico-chemical properties. The results of this study are compared with those obtained for other molecular fragments, and are rationalized in terms of existent theories.

Liquid crystalline properties of dissymmetric molecules IV. The substituent effect on thermal properties of nematic and smectic A phases in three aromatic ring systems with ester linkages

This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH3, CH3, OC8H17, C8H17, halogens, CF3, OCF3, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis.

THE TRANS-1,4-CYCLOHEXYLENE GROUP AS A STRUCTURAL FRAGMENT IN LIQUID CRYSTALS

In this review the effect on physico-chemical and electro-optical properties of the introduction of the trans-1,4-cyclohexylene fragment into the molecular core of liquid crystals is discussed, rationalized in terms of existent theories, and compared with the effect of other well-known molecular fragments.

Halogenation in achiral liquid crystals: terminal and linking substitutions

The effect on the physico-chemical properties of achiral liquid crystals of introducing halogen atoms into their terminal and linking groups is discussed and rationalized in terms of existing theories; a comparison is made with the corresponding hydrogenated and other well-known groups.

X-ray study of the nematic and smectic A phases of the cyano-substituted pyridines

Abstract We report an X-ray study of lamellar ordering in the nematic and smectic A phases of a homologous series of polar liquid crystals, the 2-(4-alkylphenyl)-5-cyanopyridines (nCP). Experiments were carried out using a diffractometer with a linear position sensitive detector. In the nematic and smectic A phases of the nCP and their mixtures with non-polar 4-n-butyl-4′-methoxyazoxybenzene two types of layering were found. One corresponds to the fluctuations of the smectic density wave with a monolayer wavevector q 1, and the other is due to the partial bilayer fluctuations with the incommensurate wavevector q 2 ≠ q 1/2. The temperature dependences of the X-ray scattering intensity and the longitudinal correlation length for both types of layering in the nematic phase are presented. The critical behaviour in the vicinity of the smectic A-nematic phase transition occurs for a fluctuation mode, either q 1 or q 2, depending on the position on the liquid crystal phase diagram. The influence of the molecular...

Pyrimidine as a Structural Fragment in Calamitic Liquid Crystals

The effect on the physicochemical and electro-optical properties of introducing the pyrimidine ring into the molecular structure of calamitic liquid crystals is discussed and rationalized in terms of existent theories; a comparison is made with the corresponding nitrogen-containing six-membered ring derivatives and 1,4-phenylene derivatives.

Alkoxylation in achiral calamitic liquid crystals

This review examines in some detail the effect on physico-chemical and electro-optical properties of introducing alkoxy groups into the molecular structure of achiral calamitic liquid crystals. The results of this study are compared with those obtained for the corresponding compounds having alkyl and other groups, and are rationalized in terms of existent theories.

Furan as a Structural Fragment in Liquid Crystals

The effect of the introduction of the furan and furan-based systems into the molecular structure of liquid crystals on the appearance of the mesophases and their physico-chemical properties is discussed and compared with that of other well-known molecular fragments.