V. A. Batyuk

Cage effect in reactions of free radicals formation and recombination in nematic and cholesteric liquid crystals

Abstract The kinetics of free radical formation during thermal decomposition of AIBN and free radical recombination in nematic 5CB-50CB mixtures and cholesteric ChOl-ChPel mixtures has been studied. The effect of orientational order of the systems on probabilities of radical escape and their recombination has been found.

Kinetics of the reduction of nitroxyl radicals by hydrazo compounds in a nematic liquid crystal

Abstract The kinetics of thermal bimolecular reactions of nitroxyl radicals with hydrazo compounds have been studied in a nematic liquid crystal. The experimental reaction rate constant in the pretransition region of the isotropic phase and in the mesophase has been found to show a positive deviation from the Arrhenius dependence obtained in the isotropic phase at higher temperatures. A method is proposed for a quantitative description of the temperature dependence of the experimental rate constant in the mesophase, based on the assumption of a decrease in the activation energy in the nematic phase, as compared with the isotropic phase. Consideration is given to the influence of nematic ordering on the activation energy of the reactions studied, conforming to the values of the parameters found from the experimental data. Models accounting for the existence of local ordering fluctuations are proposed for a quantitative description of the temperature dependence of the experimental rate constant in the isotr...

Low Temperature Solid States of Mesogenic Alkyl- and Alkoxy-Cyanobiphenyls and Nitroxide Formation Kinetics

Abstract Four low temperature solid states of long chain alkyl- and alkoxycyanobiphenyls (n= 5−8) have been obtained by special crystallization technique. The peculiarities of local molecular ordering and molecular dynamics in these phases are discussed on the basis of DTA- and kinetic data. Thermal behavior and molecular dynamic properties of liquid crystalline systems at low temperatures are of great interest. Lowering the temperature led to stabilization.

Phenomenological Approach to the Description of the Dimerization Kinetics in Nematic Mesophase

Abstract The expression has been obtained, which determines the observed reaction rate constant in the nematic mesophase as a function of scalar liquid crystal order parameter. The expression includes the experimentally obtained parameters. It has been used for the estimation of the rate constants for 2-methyl-2-nitrosopropane at selected temperatures in nematic liquid crystal MBBA.

Photoinduced Formation of Nitroxides in Partially Disordered Solid Phases of Plastic and Liquid Crystals

Abstract The kinetic features of photoinduced nitroxide formation from 2-methyl-2-nitroso-propane in a number of plastic crystals (PC: cyclohexane, cyclohexanone, cyclohexanol, 1,1,1-trichlore thane, tert-butylchloride, tert-butylamine) and liquid crystals (LC: 5CB;50CB;70CB;80CB) have been studied by ESR at low temperatures. It was shown that in crystal phases of LC′s and in complete ordered phases of PC′s the nitroxide formation quantum yields differ from zero even at temperatures which are 100–150K lower than melting points of the systems. The kinetic consequences of some orientational and positional degrees of freedom are discussed.

The Kinetic and Diffusion Regimes of the Reduction of Nitroxide by Hydrazobenzene in Frozen Liquid Crystal Materials

Abstract A kinetic model of thermal bimolecular reactions in frozen nonhomogeneous liquid crystalline systems has been proposed.

The structure effects on the thermal bimolecular reaction kinetics in frozen MBBA and MBBA:EBBA mixtures

Abstract The reduction of the nitroxyl radical by hydrazobenzene has been studied in frozen nematic liquid crystals by ESR method. The spectral and kinetic data are evidence that heterophase samples with nonuniform reagents distribution are formed at the experiment temperatures. The reaction kinetics depends on sample phase structure transformation.

The Phase-Structural Transitions in Liquid Crystalline Alkoxycyanobiphenyls and The Kinetics of Nitroxides Formation

Abstract The kinetics of photoinduced nitroxides formation has been studied by ESR in mesogenic alkoxycyanobiphenyls 60CB, 70CB, 80CB and their mixtures in temperature range 173-383 K. The nitroxide formation effectively takes place in isotropic, nematic, smectic and solid states of the systems. The reaction kinetics is sensitive to the phase structure on the molecular level.

Enzymatic Oxidation of Quinolphosphate in the Presence of Lyotropic Liquid Crystals

Abstract Enzymatic oxidation of quinolphosphate and hydrazobenzene in the presence of lecithin is discussed. To understand the dependence of the oxidation rate on the lecithin concentration, orientation of the reagents on the liposome surface and transfer of the enzyme from one vesicle to another on their collision should be taken into account.

Formation of Di-Tert-Buthylnitroxide Radicals in Liquid Crystals Studied by ESR

The photolysis of 2-nitroso-2-methylpropane in the nematic liquid crystals (in MBBA and in 4-methoxy-4-hexyloxyphenylbenzoate (MHOPhB) has been studied in isotropic phase, in liquid crystalline phase and in frozen state. MBBA was found to have negative temperature coefficient (E = −3.5 kcal/mole) in liquid crystalline phase. In all the three phases of MHOPhB low temperature dependence of photolysis rate (E = 1.9 kcal/mol) was observed.