V. E. Agabekov

Photochemical transformations of sulfophthaleine dyes in thin film state

Abstract Photochemical transformations of phenol red, thymol blue, bromthymol blue, bromcresol purple and bromphenol blue were studied in a thin film state by spectroscopy techniques. Sulfophthaleines in thin film state have been shown to be a mixture of three associated tautomeric forms, lactone, quinone and zwitterion, which differ in their stability in vacuum and in air, the ratio of concentrations of the tautomers being dependent on the chemical structure of the dyes. Reactions in the dark in sulfophthaleine films led to new equilibrium tautomer concentrations, the stable forms being predominant; the dark reactions are accelerated with an increase in temperature. Simultaneous photochromic transformations (equilibrium first-order reaction) and photobleaching and photoetching (non-equilibrium zero-order reactions) occur during photoirradiation of sulfophthaleine films. The concentration of paramagnetic centers (PMCs) in unexposed film is practically equal to that in powders and substantially higher than that in UV-exposed films. A synchronous change in concentration of the zwitterion form, in the quantity of oxygen consumed, and in the concentration of PMCs is observed in photoirradiated sulfophthaleine layers.

Effect of nanodisperse carbon fillers and isocyanate chain extender on structure and properties of poly(ethylene terephthalate)

The effect of diisocyanate chain extender (CE) on the mechanical, rheological, and relaxation properties, as well as on molecular weight and crystallizability, of starting poly(ethylene terephthalate) (PET) and its composites containing carbon nanomaterials (CNM) such as carbon nanotubes (CNTs) and commercial carbon (CC) has been studied. The composites were compounded in molten PET using twin-screw extruder (screw diameter 35 mm; L/D = 40). To improve the distribution of CNM in the polymeric matrix (before introduction into the melt), they were blended with PET powder and subjected to an ultrasonic treatment in methylene chloride. The salient features of the materials structure were estimated based on DSC and relaxation spectrometry (dynamic mechanical analysis) data. It has been found that CNM additives partly suppress the PET-chain extension reactions which take place during interaction between macromolecular end groups and CE. Besides, both CNT and CC favour crystallizability of the modified PET owing to nucleation of the crystallization process. The influence of CNT appears to be more effective than that of CC. Enhancements in true mechanical strength and deformability of PET/CE/CNM composites, as against PET/CE materials, were found to be most clearly exhibited by the CNT-containing composites.

Optical properties of polyvinyl alcohol films modified with silver nanoparticles

Polyvinyl alcohol (PVA) films modified with Ag nanoparticles and orientated by single-axial tension do not possess dichroism at light passing as well as the film that is cross-linked under the action of bichromates and UV light. These films are double-ray refracting and behave themselves as phase plates that transform linearly polarized incident radiation to elliptically polarized one. The film of latter type has optical properties of reflective diffuse polarizer with polarizing ability ∼0.8 in the range of observation angles from 20° to 80°.

P-134: New Mechanism of Photoalignment Based on Reversible Intermolecular Bonds

We present new mechanism of liquid crystal photoalignment based on reversible intermolecular bonds (hydrogen bonds or metal-oxygen bonds) between dye molecules. This mechanism differs from known before and possesses temporal stability of photoinduced alignment against thermal disordering at room temperature. Predicted photoalignment dye was synthesized and verified in experiment.

Anisotropy of polarizing polyvinyl alcohol films

The anisotropy ofthe polarizing films produced on the base of polyvinyl alcohol and dichroic dyes has been studied by visible dichroism and heat conductivity anisotropy methods. The influence ofstructure and content ofthe dye as well the stretch ratio of films on the orientation factors has been investigated. The comparative results allowed to evaluate a degree of arrangement of polymer chains and dye molecules in anisotropic films.

Thermal and Oxidative Transformations of Polycyclohexadiene in the Solid Phase and Solution

Abstract The paper deals with the investigation of polycyclohexadiene oxidation mechanism in the solid phase and solution so as its inhibition. The schemes of these processes are proposed and kinetic parameters have been determined. Polymer degradation in solution is associated with transformation of peroxide radicals which lead to the formation of low-molecular products in the initial oxidation stage.

Broad band thermostable polarizing film based on poly (vinyl alcohol), a quinoline derivative and ZnO nanoparticles

In the present study, for the first time on the basis of polyvinyl alcohol (PVA), dichroic dyes: (sodium 4-[(4E)-4-[(2E)-2-(2-chloro-3-{(E)-2-[1-(4-sulfonatobutyl)quinolinium-4-yl]ethenyl}-2,3-dihydro-1H-inden-1-ylidene)ethylidene]quinolin-1(4H)-yl]butane-1-sulfonate) (I), 6-amino-4-hydroxy-3-((4-(phenyldiazenyl)phenyl)diazenyl)naphthalene-2-sulfonic acid (II), and Chicago Sky Blue (III) broad band thermostable polarizing PVA-films were created. The obtained polarizing PVA-films had polarizing efficiencies (PEs) in the range of 97–99% in UV-Vis (300–695 nm) and PEs of 90–96% in the near IR (819–855 nm) regions of the spectrum. The photostability of the films could be improved by ZnO nanoparticles (average length ∼ 1 μm and diameter ∼ 85 nm) incorporated in a polymer matrix. Apparently, ZnO NPs act as a stabilizer in the photochemical process of dye degradation. During the study, it was established that oriented broad band PVA-films are a phenomenon of the anisotropy of thermal conductivity (λ‖/λ⊥). This is very important for the existence of thermostable polarizing PVA-films. It was also found that in the films the thermal conductivity in the direction of orientation (λ‖) was higher than in a direction perpendicular to the orientation (λ⊥).

Effect of cis/trans-isomerisation on photoalignment of azo dyes

Using potassium 5-[{4′-[(5′-carboxy-4′-hydroxy-2′-methylphenyl)diazenyl]biphenyl-4-yl}diazenyl]-2-hydroxy-4-methylbenzoate and potassium 3-[{4′-[(3-carboxy-2,4-dihydroxyphenyl)diazenyl]biphenyl-4-yl}-diazenyl]-2,6-dihydroxybenzoate as examples, cis/trans-isomerization of azo dyes in solutions and dynamics of their photoalignment in thin film under irradiation with polarized light were studied.

Spectral and electroluminescent properties of divinylbiphenylyl

The results of studies of the spectral, luminescent, and electroluminescent characteristics of four linear divinylbiphenylyl derivatives are presented. All the compounds under study fluoresce effectively in solutions and thin films in the blue spectral range. For thermally vacuum-deposited films, it is possible that absorption and luminescence spectra change due to aggregate formation. The studied biphenyl derivatives can electroluminesce in simple single-layer devices with a low (4 V) threshold voltage.

Vacuum-deposited thin films of 3-methacryloyloxy-9-diethylamino-5 5-dicyanomethylene-5H-benzo[a]phenoxazine

Abstract The physicochemical properties of 3-methacryloyloxy-9-diethylamino-5-dicyanomethylene-5 H -benzo[ a ]phenoxazine and its vacuum-deposited thin films as well as its modified thin films (phase and chemical compositions, film microstructure) have been studied. Changes in the vapour phase content of the phenoxazone-5 derivative have been investigated as a function of the boat evaporator temperature. The chemical structures of the transformation products have been established. Thin films of 3-methacryloyloxy-9-diethylamino-5-dicyanomethylene-5 H -benzo[ a ]-phenoxazine show good light-sensitive and masking properties and are suitable for submicron patterning under UV exposure at λ = 266 nm .