Preparation and optical properties of composite materials based on polybenzimidazole and silver nanoparticles

Rigid-chain heat resistant polymers (with poly-2,2'-p-oxydiphenylene-5,5′-bisbenzimidazole as example) were impregnated for the first time with a silver-containing precursor in formic acid and in supercritical carbon dioxide. A procedure allowing the precursor reduction to silver nanoparticles both throughout the volume by thermal annealing of the films in the temperature interval 100–150°С and in the targeted mode using lasers operating at 405 and 532 nm was developed. It opens prospects for developing a process for production of heatresistant optical gratings and light guides. The reduces nanoparticles and their agglomerates have the size in the interval 50–200 nm and give a plasmon band in the range 450–460 nm.     

Degradation of physicomechanical properties of epoxy nanocomposites with carbon nanotubes upon heat and humidity aging

The dependence of the physicomechanical properties of epoxy nanocomposites subjected to heat and humidity aging on the type of covalently functionalized carbon nanotubes and on the uniformity of their distribution in the epoxy matrix was studied. Two types of carbon nanotubes were used: those modified with carboxy and amide groups. The elastic modulus, bending deflection, and ultimate bending strength for the initial epoxy nanocomposites with carbon nanotubes and for those subjected to heat and humidity aging were determined. The epoxy binders modified with carboxylated carbon nanotubes are more resistant to the action of aging factors. The presence of aggregates of carboxylated carbon nanotubes in the epoxy matrix positively influences the preservation of physicomechanical properties of the composite subjected to heat and humidity aging. Microscopic examination revealed structural features of the epoxy nanocomposite and their effect on the resistance of the composite to the heat and humidity aging.     

Distribution of Zinc Oxide Nanocrystals in a Polymer Film

The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter.     

Deposition of protective-decorative coatings onto aluminum alloys

Technique for deposition of a nickel coating onto various aluminum alloys was developed. This coating can be used both independently and as a sublayer under multilayer coatings and, in particular, under those of nickel, tin–bismuth, lustrous nickel, and lustrous chromium. The technique includes anodization, chemical treatment, and electrodeposition of nickel in a special solution. The working modes of the anodization electrolyte were chosen and the necessity for a preliminary chemical treatment of the oxide film being formed was substantiated. A composition of the acid electrolyte for the subsequent nickel plating was developed with buffer and improving additives. The thus deposited electroplated nickel coatings exhibit a high adhesion to the aluminum base without additional thermal treatment. This makes it possible not only to reduce the technological time for deposition of the subsequent multilayer coatings, but also to fully automate the whole process.     

<Emphasis Type="Italic">peri</Emphasis>-cyclization of 11-aroylmethyl-2,3,4,5-tetrahydro[1,3]-diazepinobenzimidazoles into 2-aryl-3,4,5,6-tetrahydro-2a,6a,10b-triazabenzo[<Emphasis Type="Italic">a</Emphasis>]cyclopenta[<Emphasis Type="Italic">cd</Emphasis>]azulenium bromides

11-Aroylmethyl-2,3,4,5-tetrahydro[1,3]diazepinobenzimidazoles at heating in conc. HBr suffer a peri-cyclization with the closure of an additional imidazole ring involving the carbonyl group of ketone and the nitrogen atom of the diazepine ring affording previously unknown 2-aryl-3,4,5,6-tetrahydro-2a,6a,10btriazabenzo[a]cyclopenta[cd]azulenium bromides.     

New chalcones containing carbazole and 3,4-ethylenedioxythiophene fragments

Russian Journal of Organic Chemistry - Acylation of 9-(2-ethylhexyl)carbazole with acetyl bromide in the presence of tin(IV) chloride gave 3-acetyl- and 3,6-diacetyl-9-(2-ethylhexyl)carbazoles...     

Halocyclization of 2-allyl(propargyl)sulfanyl-6-aminopyrimidin-4(3H)-ones

Russian Journal of Organic Chemistry - The alkylation of 6-amino-2-thiouracil with allyl, methallyl, and propargyl halides in the presence of bases gave 2-[allyl(methallyl,...     

Dynamic structure of organic compounds in solution according to NMR data and quantum chemical calculations: II. Styrene

The dynamic structure of styrene has been studied with the goal of obtaining detailed information on the internal rotation parameters. A potential energy surface has been constructed for the rotation of the vinyl group about the single bond in terms of the second-order Møller–Plesset perturbation theory with aug-cc-pvtz basis functions, and conformational dependences of ⁿ J _HH have been calculated at the FPT DFT (B3LYP) level of theory with basis functions of the same type. The vibration-averaged coupling constants have been compared with the experimental values reliably determined in this work. A high efficiency of the proposed dynamic model for structural studies of organic molecules with ultrafast internal rotation dynamics has been demonstrated.     

Determination of the heat resistance of polymer construction materials by the dynamic mechanical method

Russian and foreign standards for the techniques for the determination of the heat resistance of polymer materials are analyzed and the incorrectness of their use for polymer construction materials is shown. The determination of the heat resistance by the low-frequency dynamic mechanical method based on the temperature derivative extrema of the dynamic modulus of elasticity and the dynamic loss modulus under the transition of polymer matrices from the glassy to the highly elastic state is experimentally substantiated for multicomponent polymer compositions with dispersed or fibrous fillers.     

Adaptive symplectic conservative numerical methods for the Kepler problem

We suggest and substantiate a unified form of a family of adaptive conservative numerical methods for the Kepler problem. The family contains methods of the second, fourth, and sixth approximation order as well as an exact method. The methods preserve all the global properties of the exact solution of the problem. The variable time step is chosen automatically depending on the properties of the solution.