Том 79, № 6 (2017)

Literature data on the effect of the scale factor on the structure and properties of polymers have been analyzed. Two modes of the scale factor have been revealed. The first mode is related to the sizes of a polymer phase. This factor manifests itself when the polymer phase sizes become comparable with the sizes of a macromolecular coil. The second mode is directly associated with the sizes of a polymer sample and becomes detectable when investigating bulky polymer samples. The scale factor has been shown to substantially affect the structure-related mechanical behavior of loaded polymers, in particular, the stress–strain curves characterizing glassy polymers.

A method has been developed for the preparation of a stable “pure” silver hydrosol containing nanoparticles with an average size of 10 nm and stabilizing carbonate ions. The method consists in the photochemical reduction of silver ions with oxalate ions, which simultaneously generate carbonate ions. Optical spectroscopy, electron microscopy, and dynamic light scattering are used to study the hydrosol

The feasibility of using an amphiphilic photoactive derivative of aminoanthraquinone (C18) as both a local solvatochromic probe reporting its position in a micelle and a component of an analytical supramolecular unit in mixed micelles based on a nonionic surfactant, Triton X100, has been considered. The solvatochromism of the 1,8-anthraquinone derivative (C18) has, for the first time, been investigated. Dipole moments of C18 molecules have been determined within the frameworks of the Lippert–Mataga, Kawski, and Reichardt approaches. It has been found that the Δμ values, as calculated with the help of the first two approaches and the Onsager radius, which is, for C18, equal to 5.8 Å, are markedly higher than the value obtained in terms of the Reichardt model. Possible reasons for discrepancies, which arise between experimental data and theoretical predictions when analyzing the solvatochromic properties of dyes, have been briefly discussed. C18 has been employed as an example to show that, for chromophores capable of donor–acceptor interactions, the use of protic solvents is more reasonable, because they ensure realization of a wider spectrum of interactions with a probe, among which the van der Waals interactions play an important role. Therewith, polarization effects, rather than charge separation, make a substantial contribution. In the case of amphiphilic chromophores, “enveloping” of polar groups with hydrocarbon chains decreases the local dielectric permittivity and the probability of intermolecular donor–acceptor interactions (hydrogen bonding). The character of the microenvironment of C18 reporter in micelles has been determined with the use of the “relative polarity parameter” proposed in this work. This parameter makes it possible to compare results obtained for different models of solvatochromism. It has been shown that the characteristics of C18 microenvironment in micelles correspond to those of water–alcohol solutions, with the chromophoric moieties of dye molecules located in the polar region of a micelle, this region being formed by hydrated ethylene-oxide chains of Triton X100. Polar receptor groups of C18, which face the aqueous phase, complete the hydrophilic shell of a micelle, while hydrocarbon chains of both components compose its hydrophobic core. This structure of the normal micelle and the markedly higher intensity of fluorescence of the micellar system than that of an aqueous C18 solution make possible the analytical determination of metal ions in aqueous media.

Sorbostriction (adsorption-induced deformation) of FAS-3 microporous carbon adsorbent is investigated under dynamic conditions upon adsorption of benzene, carbon tetrachloride, and n-hexane vapors from a flow of nitrogen carrier gas at 573 K. The values of maximum deformation and corresponding times depend on the amount of an adsorptive. The peak time of sorbostriction curves is different for each substance under study, which makes it possible to use the effect of wavelike sorbostriction for the development of sensors for the control of qualitative and quantitative compositions of gas mixtures.

Poly(vinyl alcohol) (PVA) cryogels (PVACGs) are obtained and studied. The PVACGs are formed by freezing–defrosting of polymer solutions in dimethyl sulfoxide (DMSO) or its mixtures with one of the first members of the series low-molecular-mass aliphatic alcohols (methanol, ethanol, n-propanol, and n-butanol). PVA content in these solutions is 100 g/L, while the concentration of an aliphatic alcohol is varied in a range of 0.44–2.55 mol/L depending on its nature. The polymer solutions are subjected to the cryogenic treatment at temperatures 30, 40, or 50°C lower than the crystallization temperature of DMSO (+18.4°C). The frozen samples are defrosted at a heating rate of 0.03°C/min. It is shown that, in a certain range of lowmolecular-mass alcohol content in an initial system, its cryogenic treatment yields coarse-pored heterophase cryogels that have higher rigidity and heat endurance than those of DMSO–PVA cryogels. It has been shown that polymer cryoconcentration and phase separation play important roles in the formation of a cellular microstructure and an increase in the rigidity and heat endurance of PVACGs obtained in the presence of low-molecular-mass alcohols.

A model has been proposed for calculating the polarizability of a metal nanoparticle in a composite consisting of a dielectric matrix and monodisperse nanoparticles with more exact allowance for the influence of neighboring particles going beyond the Maxwell-Garnett approximation. The main attention has been focused on the imaginary component of the polarizability, which determines electromagnetic radiation absorption by a nanoparticle in the dipole approximation. It has been shown that the absorption may be noticeably enhanced or diminished depending on the incident radiation frequency.

The influence of the concentration of potassium and barium chlorides on the aggregation stability of a hydrosol of monodisperse negatively charged detonation nanodiamond with particle sizes of 4−5 nm obtained by annealing of its agglomerates in air has been studied by turbidimetry. The experimental results have been discussed within the classical and generalized Derjaguin−Landau−Verwey−Overbeek theories. The analysis of the pair interaction potentials calculated for ultradispersed particles of detonation nanodiamond has led to the conclusion that the coagulation occurs by the barrier mechanism in the primary potential minimum. It has been assumed that the structural component of the interparticle interaction energy contributes to the total balance of the surface forces.

The effects of the finite residence time of aerosol particles in the bound state and their detachment due to thermal fluctuations on the filtration efficiency of porous and fibrous materials have been investigated with allowance for longitudinal diffusion in a flow. It has been shown that the desorption of particles affects the filtration efficiency even at times shorter than residence time τ_d of the particles in the bound state, while, at t ≫ τ_d, filtration stops. Allowance for the diffusion of aerosol particles in the flow leads to a decrease in the filtration efficiency as compared with the calculations performed without taking into account the longitudinal diffusion.

In this paper, we discuss the two-layered Jeffrey-fluid model with mild stenosis in narrow tubes. The blood flow in narrow arteries is treated as a two-fluid model with the suspension of erythrocytes, leukocytes, etc., as a Jeffrey fluid, which is a non-Newtonian fluid, in the core region and plasma, a Newtonian fluid, in the peripheral region. An analytical solution has been obtained for the velocity in the core and peripheral region, volume flow rate, resistance to flow, and wall-shear stress. The effect of Jeffrey-fluid parameters, like the height of stenosis, viscosity, etc., on volume flow rate, resistance to flow (impedance), and wall-shear stress has been discussed graphically. Through the present study, it is found that the wall-shear stress and resistance to flow increases with the increase in height of stenosis and decreases with the increase in the ratio of relaxation time. It is also found that the velocity decreases with an increase in stenosis height in both the core and the peripheral region. A previous result has been also verified.