The effect of the type of solvent on the structural and dynamic parameters of polyurethane-styrene-co-acrylonitrile blends

The effect of solvents, such as THF, methyl ethyl ketone, ethyl acetate, and acetone, on the structures and molecular dynamics of polyurethane-styrene-co-acrylonitrile blends has been investigated with the use of spin-probe ESR spectroscopy, DSC, IR spectroscopy. There are slight changes in the values of molecular mobility, crystallinity, and elastic modulus of composites containing more than 50% polyurethane, and only at higher contents of the styrene-acrylonitrile copolymer are sharp changes in the structural and dynamic parameters observed in the presence of any solvent. In different solvents, the blend parameters improve in the following series: THF, methyl ethyl ketone, ethyl acetate, acetone. This outcome is determined by the thermodynamic affinities of the dissolved polymers for the solvent. It has been shown that the content of hydrogen bonds between nitrile and urethane groups (a band at 3344 cm^?1) increases with the content of styrene-co-acrylonitrile in a blend. During reversible deformation, the molecular mobility of the radical increases and further tension is accompanied by reduced mobility in the oriented blends, independently of the solvent type.     

Estimation of physical parameters of magnetic nanoparticles

The results of estimation of the magnetic moment and sizes of magnetic nanoparticles in a magnetic fluid obtained using the technique based on measuring the field dependence of the acoustomagnetic effect are considered in the paper. The samples with different magnetic phase concentrations are analyzed. The obtained results compared with the data of magnetogranularmetric analyses are studied.     

Reactions of polyfluorinated chalcones with hydrazine hydrate and phenylhydrazine

Polyfluorinated di-and triarylpyrazolines were synthesized by the reactions of polyfluorinated chalcones with hydrazine hydrate and phenylhydrazine, respectively. Reactions of benzyl-idenepolyfluoroacetophenones with phenylhydrazine resulted in the mixtures of isomeric 1,5-diphenyl-3-polyfluoroaryl-and 1,3-diphenyl-5-polyfluoroarylpyrazolines. Fluorescence properties of the synthesized triarylpyrazolines were studied.     

Microstructures and supramolecular structures of butadiene-nitrile rubbers: Paramagnetic-probe study

The chain microstructures and supramolecular structures of butadiene-nitrile rubbers are studied by ESR spectroscopy. On the temperature dependences of the rotational mobility (correlation time τ_c) of paramagnetic probes differing in size (2,2,6,6-tetramethylpiperidine-1-oxyl and 4-benzoate-2,2,6,6-tetramethylpiperidine-1-oxyl), relaxation transitions are observed. It is shown that there is a correlation between the Arrhenius parameters of rotational mobility of radicals and the copolymer composition and that different brands of rubbers differ in microstructure and supramolecular structure.     

Alkali metal and ammonium fluoro(trifluoroacetato)metallates M′[M′′3(μ3-F)(CF3COO)6(CF3COOH)3], where M′ = Li, Na, K, NH4, Rb, or Cs and M′′ = Ni or Co. Synthesis and crystal structures

A series of fluoro(trifluoroacetato)metallates were synthesized by crystallization from solutions in trifluoroacetic acid containing nickel(II) or cobalt(II) nitrate hydrates and alkali metal or ammonium fluorides: Li[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃](CF₃COOH)₃ (I), M′[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃] (M′ = Na (II), NH₄ (IV), Rb (V), and Cs (VI)), NH₄[Co₃(μ₃-F) (CF₃COO)₆(CF₃COOH)₃] (III), and Cs[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃](CF₃COOH)_0.5 (VII). The crystal structures of these compounds were determined by single-crystal X-ray diffraction. All structures contain triangular trinuclear complex anions [M ₃″(μ₃-F)(CF₃COO)₆(CF₃COOH)₃]^? (M″ = Ni, Co) structurally similar to trinuclear 3d metal oxo carboxylate complexes. The three-coordinated F atom is located at the center of the triangle formed by Ni(II) or Co(II) atoms. The metal atoms are linked in pairs by six bridging trifluoroacetate groups located above and below the plane of the [M″₃ F] triangle. The oxygen atoms of the axial CF₃COOH molecules complete the coordination environment of M″ atoms to an octahedron.     

Correlation of polymethine dye basicity with parameters of the terminal heterocyclic nuclei

The basicity values of symmetrical polymethine dyes have been compared and correlated with a variety of parameters obtained both experimentally or derived by calculations, as well as with parameters obtained by quantum mechanical methods, characterizing the electron-donating abilities of the terminal heterocyclic residues. Linear correlations have been derived for the first time between the thermodynamic and spectral characteristics of these compounds and effective parameters of the heterocyclic nuclei. The basicity has been shown to be a universal characteristic not only of the end group but of the molecule as a whole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1278–1286, September, 1989.     

Catalytic properties of Ni/SiO2 catalysts modified by group IVA elements in hydrocarbon reactions

Germanium, tin or lead additives decrease the activity of supported nickel by several orders of magnitude in the hydrogenation of benzene and hydrogenolysis of propane and n-hexane. n-Hexane is transformed to aromatization products, whereas non-modified Ni is known as a hydrogenolysis catalyst. These catalytic effects are due to changes in the electronic and chemisorption properties of nickel alloyed with inactive metals of the additives.

---

, , - . - . .