Autohesion of amorphous polymers: a fractal model

The development of shear strength of an autohesion contact for two amorphous polymers is investigated in the framework of fractal analysis. It is shown that the shear strength depends on the number of macromolecular intersections and mutual diffusion in the boundary layer. The data for both analyzed polymers are described by one equation.     

Invariant and quasi-invariant measures on infinite-dimensional spaces

Extensions of locally convex topological spaces are considered such that finite cylindrical measures which are not countably additive on their initial domains turn out to be countably additive on the extensions. Extensions of certain transformations of the initial spaces with respect to which the initial measures are invariant or quasi-invariant to the extensions of these spaces are described. Similar questions are considered for differentiable measures. The constructions may find applications in statistical mechanics and quantum field theory.     

Atom-economic Approach to the Synthesis of α-(Hetero)aryl-substituted Furan Derivatives from Biomass

An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2+2+2] and [4+2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2-hydroxymethyl-5-cyanofuran were used as starting materials. A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability.     

Structural model for the reinforcement of polymethyl methacrylate/carbon nanotube nanocomposites at an ultralow nanofiller content

The structural basis of the anomalously high reinforcement of polymer/carbon nanotube nanocomposites at an ultralow nanofiller content is studied. This effect is shown to be caused by the absence of interaction between carbon nanotubes and the related sharp increase in the interphase adhesion. From the standpoint of a nanofiller structure, the effect disappears when three critical points related to the structure of carbon nanotubes in a polymer matrix are reached. These points are a percolation threshold, an aggregative nanofiller stability threshold, and the beginning of formation of closed circular carbon nanotube structures.     

Phase transformation α → ε in meteoritic Fe–Ni alloy under shock-wave loading

We have studied microstructural deformation-induced changes and phase transformations in the material of the Sikhote-Alin iron meteorite (IIAB) after loading by spherically converging shock waves. The results obtained by the method of electron backscatter diffraction, as well as the data of local chemical analysis unambiguously indicate the presence of regions experiencing polymorphic α → ε and ε → α transitions in the loaded sample.     

Energy of planar defects in the Ni<Subscript>3</Subscript>Al phase: Theory and experiment

The Ni₃Al phase with an L1₂ surperstructure exhibits a clearly pronounced positive temperature dependence of the yield stress. The nature of this phenomenon is still not clearly understood. The temperature dependence of the yield stress under consideration is determined, in many respects, by the structure of glide superdislocations and planar defects of these superdislocations involved in the L1₂ superstructure. A critical analysis is made of the current state of the art in the solution of the problem regarding the energy of antiphase boundaries in planes of an octahedron and a cube, as well as the energy of stacking faults in the Ni₃Al phase.     

Description of mechanical properties of particulate-filled nanostructured polymer composites using fractal analysis

A number of the main mechanical characteristics (yield strength, impact toughness, microhardness) of particulate-filled polymer nanocomposites are quantitatively described using fractal analysis. The approach is used to study the main mechanical behavior features of these materials. The influence of the initial particle size of nanofiller and the degree of particle aggregation on the mechanical properties of nanocomposites is shown.     

Synthesis and Complexing Properties of Phosphorus-Substituted Pyridine-2-Carboxylic Acid Anilides

Abstract

Novel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et₃N and unsubstituted pyridine-2-carboxylic acid using P(OPh)₃ as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography.     

Particle number density and velocity distributions in laser plumes

A time-of-flight mass spectrometer with electron impact ionization facility was used in investigations of the laser plume structure. Densities and velocity distributions of positively charged and neutral species were measured 12 cm downstream of the target. Velocities of particles in a plume were measured by the retarding potential method. The combination of a skimmer and declining electric field was used to suppress the influence of charged particles during the measurement of the neutral component parameters. In the case of YBaCuO ceramic laser ablation, a strong variation of the laser-induced plume composition was observed from its head to its tail. It seems to be accounted for by the difference of the starting (phase transition) temperatures of various layers of a plume. Ions detected mainly in the head of a plume were followed by atoms, molecules and clusters in inverse succession to their appearance in the plume under the light intensity increase. The characteristic of the number density dependence upon the laser spot diameter make it clear that most of the molecules BaO and YO are the direct product of ablation. In contrast, the detected clusters with masses up to 2000 amu are the product of condensation in the expanding plume under the conditions of the experiments.     

Dynamics of the fields of counterpropagating light pulses of a few oscillations in nonlinear dielectric media

Evolution equations have been derived for the fields of counterpropagating light pulses of a few oscillations interacting with dielectric media with nonresonant dispersion and inertialess electron nonlinearity. Changes in the field structure and spectrum of a low-intensity pulse colliding with a high-intensity counterpropagating light pulse are illustrated. It has been shown that such a collision can be accompanied by the generation of radiation at multiple frequencies with a duration smaller than the durations of the initial pulses.