Molecular and conformational properties of comb-like polymers with ionically bound side chains studied in organic solvent

Conformational and dynamo-optical properties of a homologous series of poly(cetyltrimethylammonium 2-acrylamido-2-methylpropane sulfonates) with molecular masses ranging from 80 to 700?kDa were studied in chloroform solutions by viscometry, dynamic light scattering, sedimentation, and flow birefringence. The Mark–Kuhn–Houwink Equations for this polymer in chloroform were obtained; the values of hydrodynamic diameter and the Kuhn segment length as well as the value of intrinsic anisotropy of polarizability of the monomer unit were defined.     

Hybrid composites based on 3-aminopropyltriethoxysilane and nitrogen polybases

Process in which composites are formed in sol-gel systems based on 3-aminopropyltriethoxysilane and vinyl derivatives of nitrogen-containing heterocyclic compounds was studied. These products are highly dispersed and thermally stable interpenetrating polymers insoluble in water and organic solvents. Their composition and structure were examined.     

Low-field magnetic resonance in granular nanostructures

A series of (CoFeB) + (SiO₂) magnetic film samples was investigated by ferromagnetic resonance. The magnetic resonance in low fields was experimentally observed. The influence on the position and width of the low-field peak of the magnetic phase concentration in nanofilms and of the registration parameters of a spectrum were established.     

Synthesis and thermal transformation of multi-component layered double MgCo/AlFe hydroxides with hydrotalcite srtucture

A series of multi-component layered double hydroxides with hydrotalcite structure containing doubly charged magnesium and cobalt cations and triply charged aluminum and iron cations in the brucite-like layers have been synthesized by co-precipitation at variable pH. Formation of the hydrotalcite structure has been confirmed by X-ray diffraction analysis. Thermal behavior of the synthesized samples has been studied by IR spectroscopy, thermogravimetry, and differential thermal analysis.     

Distribution of cations in magnetite prepared by mechanochemical synthesis

The distribution of iron cations in the crystal lattice of the Fe_3?vO₄ (v=0.153) cation-deficient spinel produced by mechanical dispersion of α-Fe₂O₃ hematite in water is investigated using x-ray diffraction and Mössbauer spectroscopy. Analysis of the Mössbauer data shows that the Fe_2.847O₄ magnetite prepared by mechanochemical synthesis is a chemically heterogeneous compound. The crystal structure of Fe_2.847O₄ is characterized by local environments of the (Fe^2.5+)₀ cations at v₀≤0.1, v₁?0.12, v₂?0.18, and v₃?0.26, which are responsible for a broad distribution of magnetic hyperfine fields with the P(H) probability maxima near 37.0, 36.0, 34.0, and 30.0 MA m^?1.     

Bifurcation analysis of Liesegang ring pattern formation

Bifurcation analysis is introduced to a prototype Liesegang ring (LR) model to explain pattern formation as an instability of a propagating plane reaction front. A theoretical criterion for the onset of patterning is derived and numerically tested. The uneven spacing law of LR bands is explained as a consequence of the time varying velocity of the moving reaction front. Suggestions for controlling pattern formation are provided.     

Synthesis of hydroxybiphenyls

Cyclohexylphenols were converted into hydroxybiphenyls via dehydration over large-scale palladium catalysts. The process involves slow reaction of the substrate with active centers of the catalyst with subsequent fast product formation and hydrogen desorption.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1337–1339.Original Russian Text Copyright © 2004 by Kuznetsova, Postnova, S. Koshel, Lebedeva, Yunkova, G. Koshel.     

Effect of H/D-isotope substitution on the solubility and solvation thermodynamics of krypton in methanol solutions of carbamide

The solubility of gaseous krypton in CO(NH₂)₂—CH₃OH (CD₃OH) and CO(ND₂)₂—CH₃OD solutions with carbamide concentrations of up to 1.5 solvomolality units (0.026 mole fractions) was measured at 278, 288, 298, 308, and 318 K and at a partial gas pressure of 101325 Pa. The thermodynamic functions of dissolution (solvation) of krypton and the standard Setchenov coefficients were calculated. The solvation of Kr molecules increases upon deuterium substitution and with an increase in the temperature and carbamide concentration. In these solutions, specific contacts between the carbamide and methanol molecules play the predominant role.     

Dependence of the enthalpy of polyvinylpyrrolidone dissolution on the composition of water-ethanol solvent at 298 K

Changes in enthalpy upon the dissolution of polyvinylpyrrolidone in a water-ethanol solvent were determined. The effect of temperature, the molecular mass of the polymer, and the ethanol content in the mixed solvent on these characteristics was demonstrated.