V. E. Bozhevol’nov

Positronium annihilation data and actual free-volume distribution in polymers

Determination of the size distribution of free-volume holes in solids, in particular, polymers, is an important physicochemical problem. The positron annihilation technique has been proposed for this purpose. The central point in this technique is the quantitative interpretation of data, especially, for substances with a high specific surface area. A developed free-volume system in open-pore membrane materials, such as poly(trimethylsilylpropyne) PTMSP and the spirocyclically bound benzodioxane polymer PIM-1, and polymeric sorbents (hypercrosslinked polystyrenes) makes it possible for the first time to compare the sorption characteristics and positron annihilation data on the character of size distribution of nanopores in these polymers. In combination with the results of mathematical simulation of the structure and radiothermoluminescence measurements, the array of data indicate the structural inhomogeneity of the test amorphous materials. It was shown that this inhomogeneity in relation to the positron annihilation technique is expressed in the insufficiency of the representation of the orthopositronium decay curve by one component that takes into account the Gaussian lifetime distribution (symmetrical pore size distribution) and in the necessity of use of several decay components. The feasibility of revealing a nonrandom character of pore size distribution gives the positron annihilation technique an advantage over other approaches (inverse gas chromatography, 129Xe NMR) to investigation of nanopores in polymers.

Use of solid-phase inhomogeneities to increase the efficiency of ultrasonic therapy of oncological diseases

Authors’ concepts on the use of solid-phase sonosensitizer nanoinclusions in biological structures as ultrasonic energy concentrators in the therapy of oncological diseases are developed. The possibility of directed synthesis of nanoparticles and their aggregates in tumor tissue depending on its growth features is discussed. It was found that acoustic effects in polymer structures containing solid-phase inclusions depend on the nature of these inclusions and their bond with the polymer matrix. Using model gel systems, it was shown that solid-phase sonosensitizers enhance local thermal effects and amplitude-dependent scattering of ultrasound during its propagation in gel. Experimental studies on animals showed that the ultrasound exposure of malignant tumors containing nanoparticles of gold and some complex compounds results in a significant therapeutic effect.

Localization of acoustic energy in gel systems on solid-phase inhomogeneities

The thermal effects of ultrasound on an agarose gel containing nanoparticles of iron(III) hydroxide and barium sulfate are comparatively studied. The agarose matrix is shown to interact differently with iron(III) hydroxide and barium sulfate. The relative change in ultrasound absorption due to modifier particles located in the gel is estimated. The highest thermal effect is observed for systems in which modifiers are located on separate elements of the matrix bulk. Production of “containers” with ultrasound-controlled drug release on the basis of thermosensitive gels containing solid-phase inclusions is discussed as an example of possible application of the effects described.

Secondary nucleation in the formation of methane crystal hydrate

The kinetic data on crystallization and a morphological analysis of a layer of CH4 · 6H2O hydrate crystals formed on the surface of water as a result of methane absorption showed that secondary nucleation occurred during hydrate crystallization. The mutual arrangement of crystals in the layer revealed photographically in situ was evidence that part of nuclei produced on the surface of previously formed crystals went away from the surface into solution and grew there independently of “mother” crystals, although the probability of such transfer into an immobile solution remained low. In view of this, a model of crystal growth generating secondary crystals was developed.

Combined method of ultrasound therapy of oncological diseases

The experience of the joint research by the Department of Chemistry, Lomonosov Moscow State University, and the Federal State Budgetary Scientific Institution “N.N. Blokhin Russian Cancer Research Center” (FSBSI “N.N. Blokhin RCRC”), on the application of medium-intensity ultrasound in combination with chemotherapy and sonosensitizers in the treatment of cancer diseases was summarized. A cycle of preclinical trials showed that the method allows enhancing the damaging effect of ultrasound on the tumor, while no metastasis-promoting and toxic effects are exerted. The combined method is being currently tested in clinical trials.

The problem of optimal technologies for functional materials

AbstractThe work analyzes the possibility of treating the production of a functional material as the realization of the stage of separation of the substance forming the material from a supersaturated medium and the stages of physical and chemical modification of the separated substance. The key kinetic equation of variation of the distribution function of states of the particles of the substance at each stage is formulated, considering the discrete nature of the nucleation, growth, and aggregation of particles. Solutions to continuous versions of the kinetic equation with regard to each stage are given. The conception of the path

Thermoresponsive hydrogels with ultrasound-controlled properties

\vec Z(\vec g)

Variability of nanosystems

of obtaining the material is introduced in the form of the coupling function of the target properties