Synthesis, mesomorphism, and unusual magnetic behaviour of lanthanide complexes with perfluorinated counterions

Lanthanide complexes of the Schiff base ligand 4-dodecyloxy-N-hexadecyl-2-hydroxybenzaldimine and with perfluorinated alkyl sulfate counterions were synthesised. All of the metal complexes show a smectic A mesophase. The viscosity of this mesophase is much lower than that of analogous compounds with nitrate or alkyl sulfate counterions. The behaviour of these new highly anisotropic molecular magnetic materials was studied using high-temperature X-ray measurements in an external magnetic field and temperature-dependent magnetic susceptibility measurements. The mu(eff)-versus-temperature curve is more comparable with those expected for nematic phases than for smectic phases. The luminescence spectrum of a EuIII compound shows that the values of the second rank crystal field parameters are very large. The huge magnetic anisotropy can be related to this strong crystal-field perturbation.     

Kinetics and consequences of "bleeding" of volatiles from plexiglas

The authors have studied the kinetics of "bleeding" during the heating of oriented and non-oriented plexiglas with accrued operating times of up to 16,000 h. They show that bleeding of the products of degradation of macromolecules from plexiglas is accompanied by a decrease in the volume of the polymer, which causes tensile stresses in the surface layers and may lead to surface cracking."Lenin Komsomol" Riga Red Banner Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 346–348, March–April, 1974.     

Investigation of the wedge pressure (Ludwik) method of testing certain plastics

The feasibility of Ludwik's method, which consists in squeezing a test piece between two wedges, as a means of determining the tensile strength of polymeric materials is demonstrated.Riga Polytechnic Institute. Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 366–369, March–April, 1971.     

Some properties of the polypropylene - aluminum system

The effect of composition on the properties (bulk resistivity, hardness, compressive deformation, density, and microstructure) of polypropylene-aluminum specimens has been investigated. The changes are not additively related with the composition. An explanation of the observations is proposed.Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 323–326, March–April, 1971.     

Buildup of defects in polymethyl methacrylate in service and their effect on its notch sensitivity

This study deals with the effect which defects built up in polymethyl methacrylate during 0–16,000 h of service have on its physicomechanical properties, fracture topography, and notch sensitivity. The trend of strength and plasticity characteristics is established as well as that of the coefficients of notch sensitivity as functions of the notch depth.Lenin Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 256–262, March–April, 1976.     

Properties of a Multicomponent MoVSbNbCeOx/SiO2 Catalyst in the Oxidative Dehydrogenation of Ethane to Ethylene

Kinetics and Catalysis - A multicomponent MoVSbNbCeOx/SiO2 oxide catalyst exhibiting high catalytic activity in the oxidative dehydrogenation of ethane to ethylene is synthesized by spray drying of...     

Preparation of Ag/HOPG model catalysts with a variable particle size and an in situ xps study of their catalytic properties in ethylene oxidation

The preparation of model silver catalysts supported on highly oriented pyrolytic graphite is described, and the effect of the Ag particle size on the catalytic ethylene oxidation into ethylene oxide, studied by in situ XPS and mass spectrometry, is considered. For a mean particle diameter of 8 nm, the adsorbed oxygen species characterized by an O 1s binding energy of 530.8 ± 0.2 eV (electrophilic oxygen) forms on the silver surface exposed to the ethylene-oxygen reaction mixture. Larger silver particles with a mean diameter of 40 nm additionally contain the adsorbed oxygen species characterized by an O 1s binding energy of 529.2 ± 0.2 eV (nucleophilic oxygen). The presence of both oxygen species on the surface of the larger particles ensures the formation of ethylene oxide, while the sample with the smaller silver particles is inactive in the epoxidation reaction. The O 1s signal at 530.8 eV is partly due to oxygen dissolved in the subsurface layers of silver.     

Molybdophosphonate clusters as building blocks in the oxomolybdate-organodiphosphonate/cobalt(II)-organoimine system: structural influences of secondary metal coordination preferences and diphosphonate tether lengths

Hydrothermal conditions have been used in the preparation of a series of organic-inorganic hybrid materials of the cobalt-molybdophosphonate family. The reactions of MoO(3), cobalt(II) acetate or cobalt(II) acetylacetonate, tetra-2-pyridylpyrazine (tpyprz), and organodiphosphonic acids H(2)O(3)P(CH(2))nPO(3)H(2) (n = 1-5 and 9) of varying tether lengths yielded compounds of the general type {Co(2)(tpyprz)(H(2)O)(m)}4+/MoxOy{O(3)P(CH(2))(n)PO(3)}z. The recurring theme of the structural chemistry is the incorporation of {Mo(5)O(15)(O(3)PR)(2)}(4-) clusters as molecular building blocks observed in the structures of nine phases (compounds 2-9 and 11). The structural consequences of variations in reaction conditions are most apparent in the series with propylene diphosphonate, where four unique structures 4-7 are observed, including two distinct three-dimensional architectures for compounds 5 and 6 whose formulations differ only in the number of water molecules of crystallization. With pentyldiphosphonate, a second phase 10 is obtained which exhibits a unique cluster building block, the hexamolybdate [Mo(6)O(18){O(3)P(CH(2))(5)PO(3)}](4-). In the case of methylenediphosphonic acid, a third structural motif, the trinuclear {(Mo(3)O(8))(O(3)PCH(2)PO(3))}2- subunit, is observed in compound 1. The structural chemistry of compounds 1-11 of this study is quite distinct from that of the {Ni(2)(tpyprz)(H(2)O)(m)}(4+)/Mo(x)O(y){O(3)P(CH(2))(n)PO(3)}z family, as well as that of the copper-based family. The structural diversity of this general class of materials reflects the coordination preferences of the M(II) sites, the extent of aqua ligation to the M(II) sites, the participation of both phosphate oxygen atoms and molybdate oxo-groups in linking to the M(II) sites, and the variability in the number of attachment sites at the molybdophosphonate clusters. Since the charge densities at the peripheral oxygen atoms of the clusters are quite uniform, the attachment of {M(2)(tpyprz)}(4+) subunits to the molybdophosphonates appears to be largely determined by steric, coulombic, and packing factors, as shown by extensive density functional theory calculations.