Formation of the ionic gold(III) complex [Au3{S2CN(CH2)4O}6][Au2Cl8][AuCl4] in chemisorption systems [M{S2CN(CH2)4O}2] n -[AuCl4]−/2 M HCl (M = Cd, Zn): Supramolecular structure and thermal behavior

The interaction of freshly precipitated cadmium and zinc morpholinedithiocarbamates with solutions of AuCl₃ in 2 M HCl is studied. In both cases, the heterogeneous reactions of gold(III) binding from solutions lead to the formation of the ionic gold(III) complex [Au₃{S₂CN(CH₂)₄O}₆][Au₂Cl₈][AuCl₄] (I), whose molecular and supramolecular structures are determined by X-ray diffraction analysis. Compound I includes centrosymmetric and noncentrosymmetric cations [Au{S₂CN(CH₂)₄O}₂]⁺ in a ratio of 1: 2. According to the manifested structural differences, the complex cations are related as conformers (cations A are Au(1) and cations B are Au(2)). At the supramolecular level, the isomeric cations form linear trinuclear structural fragments [Au₃{S₂CN(CH₂)₄O}₆]³⁺ [A...B...A] due to secondary bonds Au...S of 3.6364 Å. The anionic part of compound I is presented by [AuCl₄]^? and centrosymmetric binuclear [Au₂Cl₈]^2?, whose formation involved secondary bonds Au...Cl of 3.486 and 3.985 Å. The ultimate chemisorption capacity of cadmium and zinc morpholinedithiocarbamates calculated from the binding of gold(III) is 901.7 and 1010.4 mg of Au³⁺ per 1 g of the sorbent, respectively (i.e., each miononuclear fragment of the chemisorption complexes [M{S₂CN(CH₂)₄O}₂] participates in binding of two gold atoms). To establish the conditions for the isolation of bound gold, the thermal properties of compound I are studied by simultaneous thermal analysis. The thermal destruction process includes the thermolysis of the dithiocarbamate part of the complex and anions [AuCl₄]^? and [Au₂Cl₈]^2? with the reduction of gold to the metal, being the only final product of the thermal transformations of compound I.     

Synthesis of N-Vinylpyrrolidone-Crotonic Acid-2-Hydroxyethyl Methacrylate Terpolymers as Carriers of Biologically Active Substances

Water-soluble N-vinylpyrrolidone-crotonic acid-2-hydroxyethyl methacrylate terpolymers, potential polymeric carriers for biologically active substances, were prepared. The composition of the terpolymers was determined, their chemical structure was confirmed, and their hydrodynamic characteristics and structural features in aqueous solutions were studied.     

Using Plasma-Activated High Performance Fibers with Nanocrystalline Structure in Producing New Reinforced Composite Materials

A multifilament wet-pull-out method for estimation of physicochemical interaction between the fiber and the matrix in composite materials reinforced with high-strength high-modulus polyethylene fiber has been proposed. Controlled parameters are fiber capillary rise h and pull-out force F. The method allows one to estimate the wettability and multifilament fiber impregnation with the liquid matrix and measure fiber capillary rise and the joint strength after curing process finished. The multifilament wet-pull-out method considers a total interaction between the matrix and filaments in a complex fiber or yarn. It is the advantage of this method in comparison with the tests of individual monofilament. The method makes it possible to model the real operating conditions of CM.     

Binding of gold(iii) with silver(i) dipropyldithiocarbamate: supramolecular self-assembly (role of secondary Au…S and Ag…S bonds) and thermal behavior of the ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n

The double ionic-polymer complex ([Au(S₂CNPr₂)₂][AgCl₂])_n (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and ¹³C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S₂CNPr₂)₂]⁺ (A and B) and the discrete linear anion [AgCl₂]^–. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl₂]^– anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl₂]^– anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

     

Adhesion of Thermoplastic Matrices with Different Molecular Weights to Fibers

The dependence of the interfacial strength in polymer-fiber systems on the molecular weight (MW) of the matrix is investigated. Adhesive joints of poly(phenylene-sulfide sulfones) and polysulfones with a steel wire 150 m in diameter and glass fibers 200-300 m in diameter are examined. The MW of both polymers was controlled during the synthesis process. The shear adhesive strength was determined by the pull-out technique. For all the systems investigated, it is shown that the adhesive strength in relation to the duration t _f of their isothermal formation is described by curves with a maximum, whose values depend on the formation temperature T _f. For each polymer with a given MW, the greatest possible of these values, called optimum and denoted by _opt, are determined. It is found that _opt increases with molecular weight. It is speculated that the effect observed stems from the different packing of polymer chains with distinct lengths in the near-surface layers.     

New Potentialities in Producing Composites Reinforced with High-Strength High-Modulus Polyethylene Fibers

A concept of physical and chemical stages of interaction between the matrix and reinforcing fibers during the production of composite materials is introduced. A strong bond between these constituents is formed at the stage of chemical interaction, which is characterized by a certain value of activation energy. The activation energy of such an interaction for high-strength high-modulus polyethylene fibers used for reinforcing composites is estimated. Based on these estimates, conditions for fiber activation with cold plasma are found. The application of plasma-activated polyethylene fibers for reinforcing an epoxy matrix allows one to produce light-weight composites with high physicomechanical indices. The failure mode of such composites points to a high strength of the bond between the fibers and matrix. The data on treating the fiber surface with cold plasma above the activation energy of chemical interaction may be utilized to create new types of organic composites from other kinds of organic fibers and matrices.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

Binding of Au3+ from solutions by nickel(II) and cadmium diisopropyl dithiophosphates: MAS 31P NMR, structure and thermal behavior of the polynuclear complex [Au2{S2P(O-iso-C3H7)2}2] n

The paper deals with reactions of freshly precipitated diisopropyl dithiophosphate (Dtph) complexes of nickel(II), [Ni{S₂P(O-iso-C₃H₇)₂}₂] and cadmium, [Cd₂{S₂P(O-iso-C₃H₇)₂}₄], with the [AuCl₄]^? in 2M HCl, resulting in gold transition from the solution to the precipitate as polymeric gold(I) diisopropyl dithiophosphate. The reduction of gold(III) to gold(I) noted in both cases is due to oxidation of the relevant part of the Dtph group to bis(O,O??-di-(iso)-propoxythiophosphoryl) disulfide, (iso-C₃H₇O)₂P(S)S-S(S)P(O-iso-C₃H₇)₂. The polynuclear gold(I) complex [Au₂{S₂P(O-iso-C₃H₇)₂}₂] _n (I) was isolated on a preparative scale from the chemisorption system and studied by MAS ³¹P NMR and X-ray diffraction. The key structural unit of I is the non-centrosymmetric binuclear molecule [Au₂{S₂P(O-iso-C₃H₇)₂}₂] in which the gold atoms are connected by two bridging Dtph groups. The structure contains two types of non-equivalent binuclear molecules related as conformational isomers. Owing to the relatively weak Au-Au contacts, the neighboring binuclear [Au₂{S₂P(O-iso-C₃H₇)₂}₂] molecules are involved in an infinite polymeric chain with conformer alternation along the chain. To elucidate the conditions for the recovery of bound gold(I), the precipitates formed in the sorption systems were studied by simultaneous thermal analysis under argon. As the final product, thermolysis gives reduced metallic gold. The ability of dithiophosphate complexes to bind gold from a solution is much lower than that of dithiocarbamate complexes, which is due to oxidation of some Dtph groups to disulfide.     

Hydrocracking of vacuum gas oil in the presence of supported nickel-tungsten catalysts

The supports containing 70% Al₂O₃ and 30% β zeolite (AZ-1 and AZ-2), which differed in mixing procedures, and the Ni-W/AZ-1 and Ni-W/AZ-2 catalysts were characterized using an adsorption technique, high-resolution electron microscopy, IR spectroscopy, and X-ray photoelectron spectroscopy and tested in the hydrocracking reaction of vacuum gas oil (VGO). It was found that the supports differed in texture characteristics and surface Lewis acidity at the same composition and similar concentrations of Brønsted acid sites. The formation of Ni-W-S sulfide species on the surfaces of both of the supports occurred in different manners: multilayer Ni-W-S sulfide species were formed on AZ-1 (S _sp = 220 m²/g), whereas single-layer species were mainly formed on AZ-2 (S _sp = 380 m²/g). It was found that catalysts containing multilayer Ni-W-S sulfide species, which were characterized by a higher degree of sulfidation, provided a higher yield of diesel fuel upon the hydrocracking of VGO, whereas catalysts containing single-layer Ni-W-S sulfide species were more active in the reactions of VGO hydrodesulfurization and hydrodenitration.