Block copolymers containing polyacrylamide and polyacrylic acid: Bulk structure and hydrogen bonds system

Asymmetric block copolymers PAAc-b-PAAm (DBCs) and PAAm-b-PAAc-b-PAAm (TBCs) comprised poly(acrylic acid) blocks of constant chain length and polyacrylamide blocks of variable chain length were synthesized using RAFT/MADIX technique. Their properties in a bulk state were studied by differential scanning calorimetry and the hydrogen bond system was investigated by Fourier transform infrared spectroscopy. It was found that DBCs and TBCs possess a homogeneous amorphous structure, whose temperatures of glass transition and destruction beginning increased with growth of PAAm block length. The H-bond system between PAAc and PAAm blocks was most developed in TBC sample and formed manly by the mixed cyclic dimmers of carboxyl and amide groups.     

Investigation of Excitation of $${K}$$ Isomers $${}^{{179m2}}$$ Hf and $${}^{{180m}}$$ Hf in ( $${\gamma,\gamma^{\prime}}$$ ) Reactions

Physics of Atomic Nuclei - The weighted-average cross sections for $${}^{179m2}$$ Hf and $${}^{180m}$$ Hf population in ( $$\gamma,\gamma^{\prime}$$ ) reactions induced by gamma rays of...     

Behavior of poly(ε-caprolactone)-based diblock copolymers in a bulk state and in solution

Abstract

A series of amphiphilic MOPEO-b-PCL copolymers (DBCs), based on biocompatible methoxypoly(ethylene oxide) with M_n=4.5?kDa and poly(ε-caprolactone) of a variable chain length, was synthesized by an anionic ring-opening block copolymerization. The structural investigations, performed by DSC and WAXS methods, revealed the microphase separation in DBC bulk structure and the existence of separate amorphous regions and microcrystalline domains of MOPEO and PCL blocks. Spectrophotometry and SLS were used to study the self-assembling of DBC macromolecules in selective dioxane/aqueous solution and to determine the main micellization parameters (CMC and -ΔG°). The DBC micelles morphology and their specific aggregation in mixed solvent were shown.     

Activity study of graphite from the chernobyl NPP reactor

The content of the isotopes ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁶⁰Co, ⁹⁰Sr, ^93m Nb, ¹⁰⁸Ag, ¹³³Ba, ¹³⁴Cs, ¹³⁷Cs, ¹⁵⁴Eu, and ¹⁵⁵Eu in the GRP-2-125 graphite from the reactor of Power Unit 2 at the Chernobyl Nuclear Power Plant was measured. The results were compared with the calculations and literature data. Some regularities and correlations were revealed in the content of various radionuclides in graphite. Graphite porosity and desorption of radionuclides from graphite were studied. Original Russian Text ? M.D. Bondar’kov, D.M. Bondar’kov, A.M. Maksimenko, V.A. Zheltonozhskii, M.V. Zheltonozhskaya, V.V. Petrov, A.I. Savin, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 274–278.     

Properties of poly(vinyl alcohol)-graft-polyacrylamide copolymers depending on the graft length. 3. Benzene solubilization by solutions of the copolymer

The peculiarities of poly(vinyl alcohol)-graft-polyacrylamide copolymers (PVA-g-PAA), which are characterized by the equal average number (N=9), but various molecular weight (or length) of graft chains, in comparison with individual PAA and PVA, were investigated in aqueous medium. Sharp rise in benzene solubilization in PVA-g-PAA solutions at M_PAA higher than 4.3·10⁵ has been established. It was shown that such effect is stipulated by the destruction of intramolecular polymer-polymer complex in the copolymer and increasing the benzene binding to separate PVA-g-PAA groups by means of hydrogen bonds. The changes in the PVA-g-PAA solubilizing ability as the function of temperature were also investigated. The obtained results are discussed from the point of view of conformational transitions of intramolecular polymer-polymer complexes (intraPPC), which exist in copolymers, in dependence on the length of graft chains.     

Studies of the radionuclide content of fuel particles sampled from the chernobyl nuclear power plant’s No. 4 reactor unit

Spectroscopic studies are performed of the L _x , K _x , and ?? emanations from fuel particles sampled in 2011 inside the Chernobyl Nuclear Power Plant??s (ChNPP??s) No. 4 reactor unit. The isotope ratios for ^134,135Cs, ^154,155Eu, Pu isotopes, ^241,243Am, and ²⁴³Cm are measured. The data on ?? emitters for all radionuclides above ²⁴¹Am exhibit considerable inconsistency with the theoretically calculated values. A systematic deviation of the ⁹⁰Sr and ¹³⁷Cs ratios for the fuel component from the 1986 data is observed. Zirconium is shown to be the main radionuclide in the fuel particles.     

Prospects of Development of Radiation Technologies in Russia

The present review article describes the role of radiation technologies in various realms of human activities, including fundamental science, industry, agriculture, and medicine. The development of radiation technologies in the world and in Russia is compared. The total number of ionizing-radiation sources in the world is approximately 11 million units, most of them being radioactive sources (about six to seven million units) and x-ray facilities (about four million units). The number of high-technology facilities (such as accelerators and tomography units of various types) that employ ionizing radiation does not exceed 200 thousand units. In Russia, there are more than 153 thousand units of such instruments and facilities. They include about 64700 units employing x-ray radiation; about 79700 radioisotope devices and setups, reactors, and radioactive-waste storage facilities; and 471 accelerators. The most promising lines of development of radiation technologies in Russia are analyzed from the strategic and economic points of view.

     

Hypersatellites at <Superscript>109</Superscript>Ag, <Superscript>123</Superscript>Te,and <Superscript>147</Superscript>Pm autoionization during internal electron conversion

The formation of hypersatellites during internal electron conversion in ¹⁰⁹Ag, ¹²³Te, and ¹⁴⁷Pm nuclei has been investigated on multidimensional-coincidence spectrometers with Ge-Si(Li), Ge-Ge, and NaI(Tl) detectors. The probability of double ionization of the K shell in these nuclei is determined and hypersatellite energy shift is measured.     

Effect of absorption of low-molecular-weight compounds by some polymer flocculants

The sorption properties of the intramolecular complex - poly(acrylamide) to poly(vinyl alcohol) grafted copolymer (PVA-PAA_N) in block state were investigated with respect to a number of compounds. The relatively small molecules of phenol, phenylalanine in water solution as well as nitrobenzene in hexane are strongly absorbed by PVA-PAA_N films. The large humine acid molecules (sizes are larger by more than ≈ 10 times) are absorbed by PVA-PAA_N very weakly. It was determined the absorption influence on the character of polymer film solution. In a number of cases the oscillation of the dilution and sorption were observed when determining the critical concentrations of guest molecules in the upper layer of polymer films were achieved. The possible mechanisms of absorption were discussed.     

The peculiarities of sorbtion mechanism of phenole molecules by films of PVA‐PAAN interpolymer complex

The peculiarities of sorbtion mechanism of phenole molecules by poly(vinylalcohol) and poly(acrylamide) (PVA‐PAA_N) films are examined. An analytical model of absorbtion process based on diffusive character of penetration of phenole molecules in polymer film with the following spontaneous capturing by selftuning traps is proposed. The analytical results can be easy compared with experimental data obtained by spectrophotometry method. The comparison of theory and experiment gives the average value of resulting diffusion lenght of phenole molecule during «free» life‐time <l>∼10⁻⁶ cm.