Direct two-step synthesis of <Emphasis Type="Italic">n</Emphasis>-butyl acrylate–acrylic acid block copolymer by RAFT polymerization

A series of narrow-MMD polymers with the molecular mass from 33 × 10³ to 123 × 10³ (polydispersity coefficient 1.08–1.16) were synthesized by bulk polymerization of n-butyl acrylate [2,2′-azobis(isobutyronitrile), 60°C] in the presence of a low-molecular-mass RAFT agent, dibenzyl trithiocarbonate. Then, polymerization of acrylic acid was performed in aqueous-alcoholic solution (ammonium persulfate, 70°C) in the presence of the obtained polymers, and a series of n-butyl acrylate–acrylic acid block copolymers with the molecular masses from 22 × 10³ to 81 × 10³ (polydispersity coefficient 1.07–1.13) were prepared. In aqueous-alcoholic solutions of the synthesized copolymers, there are nanoparticles whose size varies from 5 tо 65 nm and increases with an increase in the molecular mass of the copolymer and in the concentration of water in the solvent.     

Analysis of the Results of Astroclimate Research at the Kara-Dag Radioastronomical Station in Crimea and the Possibilities for Reducing the Influence of the Atmosphere on Millimeter-Band Radioastronomical Observations

Journal of Experimental and Theoretical Physics - The results of astroclimate research at the Kara-Dag radioastronomical station (Crimea) from July&nbsp;22 to September 21, 2017, are presented....     

Calculation of thermal processes upon the laser modification of HTSC ceramics aimed at increasing the critical current

A mathematical model for the heating of a surface layer of HTSC ceramics by a CW laser beam scanned at a constant rate is considered. The calculated depths of the molten region are presented for the heating of the Bi(2223) ceramics by a CW CO₂ laser. The theoretical results are in reasonable agreement with the experimental data. The calculations can be used for the optimization of laser processing of superconducting ceramics aimed at increasing the critical current density.     

A new approach to the flash technique for the remote sensing of layered materials

A radically new technique of frontal monitoring, the sliding tangent method, is proposed, which makes it possible to determine the instant when the temperature regime on the surface of the body under study becomes regularized. Together with the regression analysis of the time-temperature relation for the surface, represented as a time series, this method provides a handy way for remote measuring of the thermophysical properties of material bodies to a high accuracy. The method is particularly attractive for investigating objects in vacuum, at high pressures and temperatures, and in other hostile conditions. This technique is of primary importance when the back side of the object to be investigated is inaccessible. Furthermore, any change at the surface or the back of a body can be detected remotely and nondestructively. The time and geometrical limitations for the suggested method are indicated.Tomsk Polytechnic Institute, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 393–400, May–June, 1999.