S. A. Kuvshinova

Features of the sorption redistribution of hydrocarbons and alcohols in a gas-supramolecular liquid crystal system

Thermodynamic characteristics of the sorption redistribution of hydrocarbons (C8–C12n-alkanes, C10H16 terpenes, xylene isomers) and alcohols (C3–C5 alkanols, butanediol-2,3, menthol) in a gas-4-(3-hydroxypropyloxy)-4′-formylazobenzene (HPOFAB) supramolecular smectic-nematic liquid crystal system are studied via inverse gas chromatography. The sorption capacity of HPOFAB with respect to nonmesogene sorbates is found to be strongly diminished due to its associated structure, especially in the smectic A phase. Great positive deviations from the Raoult law in the studied nonmesogene-HPOFAB systems are observed not only in mesophases, but also in the isotropic HPOFAB phase, which has a high selectivity to para- and meta-xylenes, in contrast to the isotropic phases of classic (non-associated) liquid crystals.

Effects of nonmesomorphic substituted benzonitriles on the dielectric properties of cyanobiphenyl liquid crystals

The effects of the cyano-substituted aromatic nonmesomorphic additives N-(3,4-dicyanophenyl)-4′-nonyloxybenzamide (I), 3,4-dicyanophenyl-4′-nonyloxybenzoate (II), 3,4-dicyanophenyl-3′,4′,5′-tris-(4″-undecyloxyphenylbenzoate)benzoate (III), and 4-(6-hydroxyhexyloxy)benzonitrile (IV) on the dielectric properties of 4-hexyloxy-4′-cyanobiphenyl and a liquid-crystal mixture E3 were studied. Dielectric anisotropy, birefringence, and orientational ordering were studied to show that monocyano derivative IV most strongly increased the dielectric anisotropy of mesomorphic compositions because of its effective incorporation into the liquid crystal matrix.

Selective and thermodynamic properties of supramolecular liquid-crystalline derivatives of azobenzene and biphenyl as stationary phases for gas chromatography

Smectic phase of formyl derivatives of azobenzene has been identified by means of polarization thermomicroscopy using a miscibility criterion. The study of dielectric properties and simulation of dipole moments and Kirkwood correlation factors have revealed that azobenzene and biphenyl derivatives containing hydroxy end group in the aliphatic terminal substituent can form supramolecules and linear associates stabilized by hydrogen bonds. The sorbents based on the studied liquid crystals have exhibited high structural selectivity with respect to isomers of various organic compounds. Thermodynamic manifestations of the specific mesogen–non-mesomorphic sorbate interactions have been revealed.

Phenyl benzoate derivatives with anisotropic molecular structure as stabilizers for formulations based on plasticized polyvinyl chloride

The photo- and thermostabilizing performance of nine phenyl benzoate derivatives with chemically active terminal substituents in formulations based on plasticized polyvinyl chloride was studied. The substituted phenyl benzoates exhibit thermal activity allowing them to withstand without decomposition the temperatures at which the polymeric formulations are processed. The potential stabilizers studied are capable of shielding the polymeric matrix from the most hazardous UV radiation. The plasticized polyvinyl chloride film samples stabilized with anisotropic phenyl benzoates surpass in the thermal stability the samples containing commercial stabilizers and exhibit good physicomechanical characteristics.

Mesogenic 4-acryloyloxy- and 4-(2,3-epoxypropoxy)phenyl 4-alkoxybenzoates

Procedures were developed which made it possible to synthesize in good yields homologs of 4-acryloyloxyphenyl 4-alkoxybenzoates (C3, C5, C7, C8) and of 4-(2,3-epoxypropoxy)phenyl 4-alkoxybenzoates (C5, C7). The substituted phenylbenzoates obtained exhibit the enantiotropic nematic mesomorphism in a sufficiently wide temperature range. The studied compounds have absorption maxima in the near UV region and a high temperature of decomposition beginning.

Selectivity and thermodynamics of the dissolution of structural isomers in the stationary phases based on nematic 4-ethyloxy-4′-(ω-hydroxyalkoxy)azo- and azoxybenzenes

Gas chromatography was used to study of the retention of xylene, methylanisole, and lutidine on stationary phases based on nematic 4-ehtyloxy-4′-(6-hydroxyhexyloxy)azobenzene, 4-ethyloxy-4′(3-hydroxypropyloxy)azobenzene, and 4-ethyloxy-4′-(6-hydroxyhexyloxy)azobenzene. A thermodynamic explanation of the structural selectivity of the liquid-crystalline phases of the considered compounds is proposed.

Adsorption and selective properties of 4-{4-[4(S)-2-methyl-1-butoxybenzoyloxy]phenyldiazenyl}benzaldehyde in gas–mesophase chromatography

Adsorption of 16 organic compounds from the gas phase by 4-{4-[4(S)-2-methyl-1-butoxybenzoyloxy]phenyldiazenyl}benzaldehyde was studied by gas chromatography. It was shown by means of differential scanning calorimetry that 4-{4-[4(S)-2-methyl-1-butoxybenzoyloxy]phenyldiazenyl]benzaldehyde is an enantiotropic polymorphic mesogen and forms smectic and nematic liquid crystal phases. Electron-donor isomers of methylpyridine and dimethylpyridine, isomers of weakly polar xylenes and cresols, and enantiomers of 2,3-butanediol and terpene hydrocarbons, capable of various types of intermolecular interactions with mesogenic aldehyde, were selected as adsorbates. Specific retention volumes of adsorbates and criteria for their separation were calculated. The effect of temperature and chemical nature of the adsorbates on their adsorption redistribution in the gas–liquid crystal system is discussed. It was found experimentally that the adsorbent based on 4-{4-[4(S)-2-methyl-1-butoxybenzoyloxy]phenyldiazeny}lbenzaldehyde exhibits high selectivity for close-boiling organic compounds of various nature and good efficiency and productivity in their separation.

Synthesis, mesomorphic and dielectric properties of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates, 4-(cyanomethoxy)-4′-alkoxyazo- and -azoxybenzenes

Preparation methods were developed for homologs of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates (C7, C8, C9), 4-(cyanomethoxy)-4′-alkoxyazo (C2, C3, C6), -azoxybenzenes (C3, C6) whose composition and structure were proved by elemental analysis and 1H NMR spectra. 4-(Cyanomethoxy) group destabilizes the mesophase, consequently, only four among the compounds obtained exhibit the thermotropic nematic mesomorphism.