V. G. Vasil’ev

Definition of the concept of polymer gel

The current ideas concerning polymer gels are outlined. The following definition of gel is proposed: a gel is a solid composed of at least two components, one of which (polymer) forms a three-dimensional network by virtue of covalent or noncovalent bonding (chemical and physical gels, respectively) in the medium of the other component (liquid), wherein the minimum amount of the liquid is sufficient for ensuring the elastic properties of the gel, although it may exceed tens to hundreds of times the amount of the polymer. It is noted that, at a high network density or high polymer-chain rigidity, the formation of fragile gels is possible. A general feature of physical gels is the existence of the yield point. Earlier results, which suggest the existence of two yield points in polymer gels, as found in studies of gelatin hydrogels over a wide concentration range, are suveyed.

Glycine-nitrate combustion synthesis of finely dispersed alumina

The possibility of synthesizing different crystalline modifications of alumina Al2O3 by combustion reactions of a mixture of aluminum nitrate with glycine has been analyzed. Aggregated powders of γ-Al2O3 that do not transform into the corundum structure after annealing at a temperature of 1000°C have been prepared. The influence of the synthesis conditions on the specific surface area, bulk density, porosity, and morphology of alumina particles has been investigated.

Synthesis of 2,3′,4′-tricyanobiphenyl derivatives and tetraphenylphthalocyanines based thereon

The nitration of 2,3′,4′-tricyanobiphenyl with subsequent transformations of the obtained product provided 4-X-2,3′,4′-tricyanobiphenyls (X = NO2, NH2, NHCOCH3, Br, I). The condensation of the initial biphenyl or its 4-X-derivatives (X = NO2, NHCOCH3, Br, I) in the presence of zinc acetate afforded the corresponding zinc complexes of tetra(4-X-2-cyanophenyl)phthalocyanines.

Electromagnetic Field Penetration through Lanthanum Manganites

The process of electromagnetic field penetration through lead-doped lanthanum manganites exhibiting colossal magnetoresistance has been studied. The measurements have been performed in a range of radio frequencies from 20 kHz to 10 MHz in the temperature interval containing a magnetic phase transition. Application of a constant external magnetic field leads to an increase in the transmission coefficient. Relative variations of the electromagnetic field transmission coefficient are several times as large as the relative change in the dc magnetoresistance. The temperature dependence of the relative change in the transmission coefficient has been studied. Variations of the transmission coefficient sharply decrease in the vicinity of the phase transition temperature, but they still remain rather large at temperatures above the Curie point.

The sound velocity, internal friction, and thermal expansion in a single crystal of La0.85Sr0.15MnO3

The results are given of the investigation of the temperature dependence of the sound velocity v, internal friction Q−1, and thermal expansion ΔL/L of a single crystal of La0.85Sr0.15MnO3 in the temperature range from 5 to 400 K. Clearly defined singularities of the elastic properties at a temperature of charge ordering Tco≈200 K are revealed. The results of X-ray diffraction studies performed at room temperature are used to determine the orientations and estimate the sizes of twins. The correlation between magnetic and structure inhomogeneities is established. Based on the results of analysis of the temperature dependence of internal friction and thermal expansion, an assumption is made of the presence in a single crystal of La0.85Sr0.15MnO3 of a structural transition in the temperature range from 15 to 60 K that has not been observed previously.

Ionomers of a new type based on sulfonated polyphenylquinoxalines

This communication is devoted to new type iono mers belonging to the class of aromatic ionogenic polymers—sulfonated polyphenylquinoxalines (SPPQ). The interest in SPPQ is due to the fact that the parent polyphenylquinoxalines (PPQ) are promising poly heteroarylenes combining high thermal characteristics and chemical stability with excellent solubility in organic solvents and good film forming properties [7]. Therefore, SPPQ formed upon polymer analogous transformation of PPQ upon sulfonation with a mix ture of sulfuric acid and oleum [8] can be considered as potential effective thermally stable polymeric elec trolytes and as the basis for the production of promis ing thermally stable aromatic ionomers for various applications.

Synthesis of berberine bromide analogs containing tertiary amides of acetic acid in the 9-O-position

9-O-Acetamide analogs of berberine bromide were prepared in 20–87% yields via reaction of the isoquinoline alkaloid berberrubine with tertiary amides of bromoacetic acid. Aminolysis did not occur during reaction of methyl-2-(9-demethoxyberberine bromide-9-yl)hydroxyacetate with secondary amines. The corresponding acid or its ethyl ester was isolated.

Reaction of several resveratrol glycoside derivatives with hypochlorites in various media

The reactions of pterostilbenoside (trans-3,5-dimethoxystilben-4′-O-β-D-glucoside) and Ar–O–Tr derivatives of resveratroloside (3,5-dihydroxystilben-4′-O-β-D-glucoside) and pinostilbenoside (3-methoxy-5-hydroxystilben-4′-O-β-D-glucoside) with NaOCl and t-BuOCl in the presence of the stable nitroxyl radical TEMPO were studied in various media. It was found that the principal product of pterostilbenoside transformation was its 2,6-dichloroderivative, a part of which was oxidized to form 2,6-dichloropterostilbene glucuronide. Trityl ethers of resveratroloside and pinostilbenoside reacted with the hypochlorites to form mixtures of products.

Sulfonated poly(naphthoylenebenzimidazole) and its modification with an alkali metal cation

A method for sulfonation of poly(naphthoylenebenzimidazole) with oleum–sulfuric acid mixture to produce sulfonated poly(naphthoylenebenzimidazole)s (SPNBIs) with different content of–SO3H groups has been developed. SPNBIs containing ≥5% sulfur are soluble in NMP and form stable solutions. It has been revealed that viscosity of SPNBI solutions in NMP increases on decreasing concentration when the content of polar sulfonic groups enhances with sulfonation degree of the initial polymer. Thus, SPNBI shows the polyelectrolyte effect. The substitution of hydrogen atoms in sulfonic groups by an alkali metal ion, potassium, has been conducted by the treatment of SPNBI powders with 5 M KOH aqueous solution under heterogeneous conditions. Potassium salts of SPNBI are insoluble in NMP. The introduction of potassium ions into SPNBI leads to the preparation of ionomers with a thermal stability higher than that of the initial PNBI.

Synthesis of ferrite spinel NiFe2O4 by thermal hydrolysis and its magnetic properties

A new thermal hydrolysis technique is proposed for synthesis of complex oxide ferrite spinels with the general formula MFe2O4, where M = Ni, Co, Cu, Mn, Zn, etc. The structural, morphological, and magnetic properties of powdered nickel ferrite NiFe2O4 obtained by the proposed technique are investigated.