Polarized Raman study of random copolymers of propylene with olefins

The polarized Raman spectroscopy is employed in the study of structural modifications in the films of isotactic polypropylene (PP) whose chain contains ethylene, 1-butene, 1-hexene, 1-octene, and 4-metyl-pentene-1, which represents an isomer of 1-hexene. It is demonstrated that the phase and conformational compositions of copolymer molecules depend on the comonomer content and the side-chain length of the second monomer. The content of the PP molecules in the helical conformation in the crystalline and amorphous phases of the copolymers monotonically decreases with increasing content of the second monomer. The decrease in the content of helical macromolecules in the crystalline phase is faster than the decrease in the amorphous phase. At a certain content of comonomers, the total content of the helical fragments decreases with increasing length of the side chain of the second monomer. The structures and Raman spectra of the copolymers of propylene with 1-hexene and 4-methyl-1-pentene are similar.     

The harmonic oscillations of a viscoelastic rod of triangular cross-section

Two exact solutions of the plane strain problem of the harmonic oscillations of a viscoelastic rod, the cross-section of which is a right triangle, are proposed. Either the normal displacement and the shear stress or the shear displacement and the normal stress of the side surface of the rod are given. Six dimensionless parameters which affect the dynamic deformation process are derived. Two parameters characterize the contribution of the viscous properties with respect to the elastic properties, two others define the logarithmic decrement of the longitudinal and shear harmonic waves, and two other parameters affect the wavelength of the corresponding wave and the velocity of motion of the wave front of these waves. The velocities of both types of waves and their wavelengths turn out to be greater than the velocities and wavelengths of the corresponding elastic waves. It is shown that, for certain values of the viscosity and the oscillation frequency, pseudo-resonance frequencies are possible which are higher than the resonance frequencies for an elastic medium.     

Analysis of the imperfection of opal-like photonic crystals synthesized on conducting substrates

The type and degree of imperfection for opal-like photonic crystals on conducting substrates have been investigated using synchrotron small-angle X-ray scattering with a microradian resolution. It has been demonstrated that self-assembly of poly(styrene) spheres by the vertical deposition method leads to the formation of a face-centered cubic structure on a mica/Au substrate and a random hexagonal close packing on a glass substrate with the In₂O₃(SnO₂) conducting coating.     

Polarization singularities in partially coherent combined beams

Vector singularities are predicted and discovered experimentally in partially polarized combined fields formed by incoherent superposition of orthogonally polarized beams. Such singularities are U contours with zero degree of polarization and isolated P points with unit degree of polarization centered at vortices of the orthogonally polarized component of the combined beam. Crossing a U contour switches the polarization state to the orthogonal one. The above-mentioned singularities are adequately described in terms of the complex degree of polarization in the Stokes-space representation. It is shown that the field elements corresponding to the extrema of the complex degree of polarization form the vector skeleton of a partially coherent nonuniformly polarized field.     

An <Emphasis Type="Italic">in situ</Emphasis> cell for investigation of the catalyst structure using synchrotron radiation

Design of a cell for in situ characterization of heterogeneous catalysts by X-ray absorption spectroscopy EXAFS/XANES and X-ray diffraction on synchrotron radiation at high temperatures in a controllable gas medium, which was implemented at the Structural Materials Science end-station installed at KCSRNT, is presented. First results on nanostructural evolution of Pt/γ-Al₂O₃, Pd/γ-Al₂O₃ and other catalysts during various treatments — oxidation in oxygen, reduction in H₂/N₂, and annealing in vacuum — are reported.     

Growth of single crystals of B28 at high pressures and high temperatures

A method of the high-pressure high-temperature synthesis of single crystals of orthorhombic high-pressure boron B₂₈ from metal solutions is presented. The method is based on the high-pressure multi-anvil technique. The feasibility of single-crystal growth was demonstrated in a number of experiments conducted at various pressure–temperature conditions with various precursors including β-boron of 99.99% purity and various metals (Cu, Au, and Pt) used as fluxes and capsule materials. It was found that after dissolution in metals at high pressures and high temperatures, boron crystallizes in the form of single crystals at low temperature. The process is accompanied by chemical reactions resulting in the formation of borides. The maximum length of the B₂₈ crystals achieved is ∼100 μm.     

Magnetodielectric composites based on functionalized polyphenylene sulfides containing iron nanoparticles

Preparation of iron-filled polyaminophenylene sulfides and polyhydroxyaminophenylene sulfides by the metal vapor procedure was studied. Nanocomposites based on these metal-containing polymers and epoxy-isopropylidenediphenol oligomers (ED-20) were prepared and their composition, properties, and structure were studied by X-ray diffraction and thermogravimetric analyses, and thermomechanical methods. The magnetic and dielectric properties of the materials were determined.     

On the solution of boundary value problems of mechanics for the Poisson equation and related equations

To a boundary value problem, we assign an auxiliary problem of determining the spectrum of eigenfunctions and eigenvalues (EFV). After the main problem has been reduced to a form with homogeneous boundary conditions, it becomes possible to prove theorems about the formulas for the solution of the boundary value problem with linear equations of elliptic type for multidimensional multiply connected domains by using the spectral expansion in the Fourier series. We find conditions under which the action of second-order differential operators on the obtained solutions in the Fourier series can be computed not only in the interior of the domain but also on its boundary. But if these conditions are not satisfied, then the series for second-order differential operators do not converge on the boundary. The proposed method for the expansion in the EFV can be used not only in plane but also in spatial problems if the domain of complicated shape can be represented as a combination of bounded domains with known EFV spectra. As one of the examples, we consider the problem of torsion of an elastic rod whose cross-section consists of a rectangle and a half-disk.