Comparative study of holographic recording in cholesteric and nematic azo-containing side-chain polymers

For the first time a comparative study of holographic recording in planarly oriented films of nematic and cholesteric azobenzene-containing polymers was performed. The influence of temperature and light intensity on the values of diffraction efficiencies of holographic gratings was investigated. The kinetics of grating relaxation at different temperatures was studied. It was shown that the helical supramolecular structure of cholesteric copolymer causes a significant decrease of the diffraction efficiency in comparison with the one observed for the nematic state of the homopolymer.     

Fullerene C6 0 Aggregates in Polymethyl Methacrylate Films

The structure of aggregates of fullerene C_{6 0} introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction.     

The effect of silver nanoparticles on the phase state of comb-shaped liquid crystalline polymers with cyanobiphenyl mesogenic groups

A new approach is proposed for the preparation of a new class of hybrid polymer systems based on comb-shaped LC polymers with cyanobiphenyl mesogenic groups and silver nanoparticles with dimensions ranging from 5 to 54 nm. A correlation between copolymer composition and dimensions of the formed nanoparticles is established. As the concentration of nanoparticles in LC copolymer is increased, the resultant glass transition temperature increases, and the temperature interval of the existence of LC phase is reduced. This behavior is related to the adsorption of cyanobiphenyl and carboxylic polymer groups on the surface of silver nanoparticles. In this case, the conductivity and dielectric permittivity of the composites are also increased.     

Specific features of liquid-crystalline comb-like polymers with mesogenic groups

The results of structural investigation of the new type of the liquid-crystalline thermotropic methacrylic polymers are discussed. These polymers contain mesogenic groups as models for cholesteric, nematic and smectic types of low-molecular liquid crystals. The groups are attached to the backbone through methylene bridges of various lengths. The polymers of the first group have amorphous structure; the polymers of the second group are characterized by liquid crystalline structure and those of the third group can exist in both crystalline and liquid-crystalline states, manifesting properties of enantiotropic liquid crystals. The temperatures and heats of phase transitions have been determined. It is shown that the ability to realize the liquid-crystalline state of comb-like polymers with mesogenic groups depends on and is determined by the proceess of ordering of these groups.     

Complexes of amic acids with polar aprotic solvents. VI. System of hydrogen-bonds in complexes of amic acids and polyamic acids with amide solvents

It has been established through X-ray analysis of complexes of pyromellitedianylic acid with amide solvents that the type of the system of hydrogen-bonds and the solvate structure depend on the nature of these solvents. It is shown for solvates of poly(4,4-oxydiphenylene)pyromellite amic acid that mass spectrometric thermal analysis (MTA) may be used for the investigation of hydrogen-bonds formed in solid polyamic acid films. The MTA data may be employed to establish the mechanism of the effects of additives catalysing the solid-phase cyclodehydration of polyamic acids.

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Zusammenfassung Durch röntgenanalyse von Komplexen von Pyromellit-dianilicsäure mit Amidlösungsmitteln wurde festgestellt, daß der Typs des Systems der Wasserstoffbindungen und die Solvatstruktur von der Natur dieser Lösungsmittel abhängt. Für Solvate der Poly-(4,4-oxydiphenilen) pyromellit-amicsäure wird gezeigt, daß die massenspektrometrische thermische Analyse (MTA) zur Untersuchung von in festen Polyamicsäurefilmen ausgebildeten Wasserstoffbindungen herangezogen werden kann. Die MTA-Daten können zur Ermittlung des Wirkungsmechanismus von die Festphasencyclodehydratisierung von Polyamicsäuren katalisierenden Additionen herangezogen werden.

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, . , (4,4-) , , o , , .

     

Analogs of carbohydrate-metabolism coenzymes

Conclusions We synthesized two analogs of the natural coenzyme adenosine diphosphate glucose: N₆-methyl-ADPG and N₆, N₆-dimethyl-ADPG.For communication 11, see [1].The following abbreviations are used in this article: ADPG) adenosine-5'-diphosphate-a-D-glucopyranose; N₆-methyl-ADPG) N₆-methylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose; N₆, N₆-dimethyl-ADPG) N₆, Ng-dimethylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2514–2521, November, 1969.     

Intensities of IR bands of CH stretching vibrations and atomic charges in saturated three-membered rings

The intensities of the absorption bands of the CH stretching vibrations in the IR spectra of solutions of cyclopropane, aziridine, oxirane, and thiirane in CCl₄ were measured. Quantum-mechanical calculations of these intensities were performed.Translated from Khimiya Geterotsikhlicheskikh Soedinenii, No. 12, pp. 1612–1619, December, 1989.