Mechanical Properties and Structure of Zinc-Containing Latex-Silicate Composites

The sol-gel technology is highly efficient for improving mechanical and thermal properties of polydiene elastomers by creating in them additional inorganic networks composed mainly of silica or silicates. The incorporation of modifying Zn ions into polydiene latex-silica systems increases considerably their mechanical characteristics due to an increase of the interaction between the organic and inorganic networks. Interpenetrating polydiene-silica networks were prepared by cohydrolysis of tetraethoxysilane and zinc acetate in natural Qualitex or synthetic butadiene-styrene latexes and then by aging and drying the liquid compositions at room temperature and vulcanizing at 90°C. Their structure and properties were studied by the IR spectroscopy, TMA and by tensile testing of the prepared films. The studied system was shown to be extremely suitable for obtaining latex films with improved elastic and strength characteristics. For example, the elastic modulus values of the Qualitex films containing 2–5% SiO₂ and 0.1–0.2% ZnO, are 4–9 and 6–11 times higher than those of the films prepared without zinc and of the pure latex films respectively. The possible structure roles of zinc ions at various stages of film preparation and vulcanization are discussed on the base of the results of IR and TMA studies.     

Electron beam forming system for irradiation of large diameter cylindrical products

The report describes electron beam electromagnetic forming system, which is destined for irradiation of cylindrical long goods, specifically for PE tubes 160 mm diameter. System consists of electromagnet, power supply units, beam distributions control units, etc. for use at an electron accelerator at 5 MeV and 50 kW. The particular geometry of the magnet poles and their mutual arrangement are creating an irradiation field that allows the electrons to irradiate the surface of the product close to 90°.     

A parallel solution-phase synthesis of substituted 3,7-diazabicyclo[3.3.1]nonanes

The parallel solution-phase synthesis of a series of building blocks and combinatorial libraries based on natural bispidine scaffold has been accomplished. Key reactions include catalytic hydrogenation of the (-)-cytisine heterocyclic system, followed by alkali-mediated ring cleavage. Using this approach, a series of new bispidine core building blocks for combinatorial synthesis with three points of diversity were effectively synthesized. The libraries from libraries were then obtained in good yields and purities using solution-phase acylation reactions. Obtained combinatorial libraries of 3,4,7-trisubstituted bispidines are potentially useful in the discovery of novel physiologically active compounds.     

Benzindoles

A large amount of structural similarity between 4,5-benzindole and naphthalene and between 6,7-benzindole and indole was detected on a basis of a comparison of the absorption, fluorescence, and phosphorescence spectra of isomeric benzindoles with the spectra of indole and naphthalene. A great analogy between indole and 6,7-benzindole as compared with 4,5-benzindole is also observed during the formation of hydrogen bonds, as indicated by the shift in the absorption band of the NH group in the IR spectra of the investigated compounds in the presence of various proton acceptors.     

Ionic Mobility, Phase Transitions, and Superionic Conduction in Solid Solutions (100 ? x)PbF2-xZrF4 and Crystals K2ZrF6, (NH4)2ZrF6, KSnZrF7, and M(NH4)6Zr4F23 (M = Li, Na)

Methods of (¹⁹F, ¹H) NMR and impedance spectroscopy are used to investigate the internal mobility and ionic conduction in solid solutions arising in the system PbF₂-ZrF₄ and polycrystals KSnZrF₇, Li(Na)(NH₄)₆Zr₄F₂₃, and M₂ZrF₆ (M = K, NH₄). Factors responsible for the form of ionic motions and their energetics at 170–550 K are considered. It is established that the phase transitions in these compounds are connected with the crystal transition to a superionic state and that the high ionic (superionic) conductivity of beta phases is due to the diffusion of fluoride ions, ammonium cations, and possibly alkali metal cations. The obtained data testify to a substantial role of chainlike aggregation of anionic groupings and a variableness of structural mechanisms of formation of such chains in fluorozirconates for the development of translational diffusion in these compounds.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 573–582.Original Russian Text Copyright © 2005 by Kavun, Uvarov, Slobodyuk, Goncharuk, Kotenkov, Tkachenko, Gerasimenko, Sergienko.     

Infrared absorption spectra of cyanide complexes of group VIII metals with nitrogen- and sulphur-containing ligands

Research into the IR absorption spectra of the products of interaction between nitrosyl pentacyanide complexes of some Group VIII metals and thiourea and thiocyanate has been carried out in the region 400–4000 cm^?1.An assumption has been made concerning the formation of intermediates of the association type. The changes in the spectra during the formation of intermediates indicate a weakening of ligand bonds with a metal-complexing agent.The data obtained for the series of cyanide complexes of Group VIII metals with heterogeneous ligands allow us to suggest a strengthening of the M-S bond between thiourea and metals in the order Os > Ni > Co ? FeThe M-NCS bond between the thiocyanate group and metals of the iron family is practically equivalent.Osmium coordinates the SCN^? group through the sulphur atom.     

Kinetics of photo-active bacteriorhodopsin analog 3,4-didehydroretinal

Kinetics of the photo-induced processes of the transient states of the 3,4-didehydroretinal (3,4-dhr) modified bacteriorhodopsin (bR) was studied by a flash photolysis method in a water suspension at room temperature. The excitation initiated a photocycle with several transient intermediates similar to the trans photocycle of native bR. The main observation of the study was that although major part (80%) of the population of the M state relaxed via the O intermediate as in natural bR, 20% relaxed directly to the bR ground state in 200 ms.     

Ion mobility,phase transitions,and ion transport in potassium-ammonium hexafluorozirconates

The mobility of fluoride and ammonium ions (180–480 K) in compounds K_{2? n} (NH4)_nZrF₆ (0.2 ≤ n ≤ 1.70) was investigated by ¹⁹F and ¹H NMR. Correlations have been found between the composition of the cation sublattice, the character of ion motions, and phase transition temperature in these compounds. The hightemperature modifications with n ≥ 0.85 of the compounds are characterized by translational diffusion of fluoride and ammonium ions and by uniaxial anisotropy of the ¹⁹F magnetic shielding tensor. The electrophysical characteristics of these compounds were studied in the temperature range 300–480 K.     

Charge separation in a nonfluorescent donor-acceptor dyad derived from boron dipyrromethene dye, leading to photocurrent generation

Boron dipyrromethene (BODIPY), which is commonly used as an energy absorbing and transferring antenna molecule, has been modified to contain an electron donor moiety, 8-(2,4,5-trimethoxyphenyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (MEOPHBDP). The photoinduced electron transfer from a 2,4,5-trimethoxyphenyl moiety to a BODIPY moiety of MEOPHBDP in acetonitrile was observed by femtosecond laser flash photolysis measurements. The lifetime of the charge-separated state of MEOPHBDP was 59 ps at 298 K. The dye-sensitized solar cells (DSSC) were prepared using MEOPHBDP with carboxylic acid (MEOPHBDP-COOH) and a reference BODIPY dye having no electron donor moiety. The photovoltaic measurements were performed using a standard two-electrode system consisting of a working electrode and a Pt sputtered electrode in methoxyacetonitrile containing 0.5 M iodide and 0.05 M I(2). The photoelectrochemical properties of DSSC with MEOPHBDP are compared with those with a reference BODIPY dye.