Ministry of science
and Higher Education of Russia
Ministry of science
and Higher Education of Russia
Annotation:
Relationships were established between the critical conversion of gel formation αс and the conditions of three-dimensional polymerization with the effect of substitution, that is, at different reactivities of functional groups of a monomer (oligomer) and a polymer (pendant functional groups). As was shown, at a high average-weight functionality of an initial monomer (oligomer) mixture, the reactions of chain transfer and chain termination exert no effect on αс. Comparison between the calculated and experimental values of αс was performed. In the living copolymerization of styrene with divinyl bisphenol, the effect of substitution is found to provide a threefold decrease in the reactivity of functional groups. This result agrees with an independent estimate as obtained from the kinetic data. This calculation apparatus may be applied for a quantitative calculation of the effect of substitution from the data on αс when the experimental measurements of αс> are performed for systems corresponding to certain kinetic criteria.
Authors: Korolev G.V., Irzhak T.F., Irzhak V.I.,
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Elibrary: https://elibrary.ru/item.asp?id=43791329
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New oligomeric salts of m-carboranedicarboxylic acid HOOCCB10H10CCOOH and metals, such as Ni, Co, Fe(II), Fe(III), Y, Sn(II), and Mn(II), were synthesized. A relationship is established between the thermal and electrical properties of oligomeric salts. The synthesized salts are complex redox systems which eliminate H2 upon thermal decomposition, reduce its own metal ion to a free metal, and acquire semiconductor properties. Upon a thermal treatment under the dynamic regime at 20-500°C in air and argon, the electrical conductivity of oligomeric salts increases by 5-11 orders of magnitude; after pyrolysis at 900°C in air, this parameter increases by 8-12 orders of magnitude. After storage for 6 months, the conductivity of pyrolyzates remains 8-9 orders of magnitude higher than that of the initial oligomeric salts. The electrical properties of composites based on oligomeric salts and CuO and an ED-20 epoxy resin were also studied. For the oligomeric salt-CuO composites, the initial electrical resistivity (pv = 107-108 Ω cm) is preserved to 300-400°C, while for the Y-CuO and Mn-CuO systems, this parameter remains unchanged to 500-550°C. The conductivity of the oligomeric salt-CuO and ED-20-oligomeric salt-CuO composites heated to 900°C in air increases by 3-12 and 11-12 orders of magnitude, respectively. The introduction of ED-20 does not reduce but, on the contrary, sometimes increases the conductivity of the system. Upon pyrolysis, the conductivity of some composites is preserved over a period of 6 months; however, for all other composites, this parameter decreases by 1-3 orders of magnitude.
Authors: Surikova M.A., Bekasova N.I., Baryshnikova E.A., Askadskii A.A., Kazantseva V.V., Buzin M.I., Kolosova T.N.,
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Elibrary: https://elibrary.ru/item.asp?id=43791330
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A series of new phenylated poly(phenylenes) soluble in a wide range of organic solvents were synthesized by the interaction of bis(cyclopentadienones) with various bis(arylethynyl)arylenes via the Diels-Alder reaction. The Mw and Mn of the synthesized polymers vary from 3.5 x 104 to 2.0 x 105 and from 7.6 x 103 to 3.3 x 104, respectively. The Tg values of poly(phenylenes) fall in the 229-345°C range, and temperatures corresponding to the 10% weight loss in air and argon are in the 530-613 and 581-642°C intervals, respectively.
Authors: Keshtov M.L., Rusanov A.L., Keshtova S.V., Petrovskii P.V., Men'shov V.M.,
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Elibrary: https://elibrary.ru/item.asp?id=43791331
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Molecular mobility in PVDF prepared through emulsion polymerization was studied with the use of dielectric spectroscopy. The formation of films from acetone resulted in crystallization without the production of spherulites, which is untypical of PVDF. Two processes were detected in the glass transition region, which merge at a high temperature into one combined process due to a difference in the activation energy. High values of both the enthalpy and the entropy of activation were found for the latter process, which are consisted with the data obtained previously for a vinylidene fluoride-tetrafluoroethylene copolymer with a similar morphology. It was shown that the activation parameters of this combined process limit the process of inducing remanent polarization in a film exposed to a high-strength field. It was assumed that another intense relaxation process exists in the region of higher temperatures. The analysis of structural data led to the conclusion that the polar αp-modification could be formed upon crystallization in the given mode, which might be responsible for the unusual rise in the intensity of this process with temperature.
Authors: Kochervinskii V.V.,
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Elibrary: https://elibrary.ru/item.asp?id=43791332
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The molecular mobility in polyimides containing long sequences of dimethylsiloxane units (from 9 to 99 units) in the main chain was studied through the proton magnetic relaxation technique. Dynamic nonuniformity of the dimethylsiloxane sequence was revealed, which was also manifested in crosslinked and filled systems. It was assumed that this phenomenon is due to segregation processes and the corresponding formation of associated structures with a lower mobility of methyl groups, wherein the proportion of dimethylsiloxane units involved in the formation of these structures decreases with increasing temperature.
Authors: Zaitseva Yu. A., Shevelev V.A., Martynenkov A.A., Svetlichnyi V.M., Kudryavtsev V.V.,
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Elibrary: https://elibrary.ru/item.asp?id=43791333
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Temperature-induced evolution in the structure of oriented fibers of two thermotropic random LC copolyesters was studied by X-ray diffraction and DSC. The copolymers contain four or five monomer components, one of which is chlorohydroquinone and the rest are the residues of hydrobenzoic, naphthalinedicar-boxylic, terephthalic, and isophthalic acids. It was shown that no transition from an orthorhombic crystalline phase to a pseudohexagonal mesophase, which is observed upon heating of the other polymers of this class, such as Vectra, Xydar, Ultrax, etc., takes place. To put it more precisely, the transition exhibits a virtual character. This implies that the phase transition could occur at ~350°C if the melting and isotropization of a material proceed much below this temperature.
Authors: Antipov E.M., Levchenko A.A., Volegova I.A., Razumovskaya I.V., Stamm M., Lemstra P.J.,
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Elibrary: https://elibrary.ru/item.asp?id=43791334
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The behavior of monomolecular and thin films of poly(dimethylsiloxane) and poly(diethylsilox-ane) spread on the subphases of ethylene glycol and its mixtures with water was studied by measuring surface pressure as a function of specific surface area per repeating monomer unit. It was shown that poly(dimethylsi-loxane) forms monolayers on pure ethylene glycol with a thickness equal to two times the thickness of a molecule occurring in a flat conformation. The surface pressure isotherm shows a second step corresponding to the formation of a layer with a fourfold thickness of the monolayer. Films cast from mixed ethylene glycol-water subphases demonstrate characteristics intermediate between those of films formed on pure water and pure ethylene glycol. Poly(diethylsiloxane) forms stable monolayers on ethylene glycol. The mechanism explaining the formation of layers on the alcohol subphase is advanced.
Authors: Belousov S.I., Godovsky Yu. K.,
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Elibrary: https://elibrary.ru/item.asp?id=43791335
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New photochromic amorphous and ion-containing comb-shaped LC polymers were prepared by the protonation of amino groups of tertiary amine, 4-(10-diethylaminodecyloxy)azobenzene, by the carboxylic groups of poly(acrylic acid). When the concentration of a photochromic additive in the composition is equal to ~29 mol %, the smectic phase is formed. For the amorphized compositions, the development of birefringence induced by laser irradiation was studied. As compared with the classical nematic comb-shaped LC polymers containing azo benzene groups, the corresponding kinetic curve describing an increase in the phase difference is characterized by an additional slow component. The above photooptical behavior may be conceivably related to the development of an LC phase as induced by the laser irradiation of the amorphized films of photochromic compositions.
Authors: Barmatov E.B., Medvedev A.V., Ivanov S.A., Shibaev V.P.,
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Elibrary: https://elibrary.ru/item.asp?id=43791336
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The ozone resistance, surface layer structure, and composition of covulcanizates of butadiene-acrylonitrile rubbers containing different amounts of acrylonitrile units with ethylene-propylene terpolymers (EPDM) were studied using the stress relaxation and FMIRIR spectroscopy techniques. The ozone resistance of the materials was shown to depend on the compatibility of the components with one another, the development of the interphase layer that determines the degree of covulcanization of the rubbers, and the EPDM network density.
Authors: Livanova N.M., Popov A.A., Karpova S.G., Shershnev V.A., Ivashkin V.B.,
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Elibrary: https://elibrary.ru/item.asp?id=43791337
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The results of experimental studies of viscoelastic properties were presented for phenol-formaldehyde polymer matrix and the related composite materials reinforced by short glass fibers with different degrees of orientation of fibers varying from complete disorder to strict orientation in the direction of orientation and in the perpendicular direction. From the experimental data, the integral viscoelastic operators of the compliance tensor were found. Using the above results, defining physical relationships were derived for a polymer composite that was considered an orthotropic body. Based on these grounds, the problem on the distribution of orientational stresses and strains in a plate with a heterogeneous orientation tensor distribution due to a nonsym-metric flow along one of the symmetry axes upon molding was solved by the Laplace integral transformation procedure. The theoretical results obtained for a model body satisfactorily agree with the experimental data.
Authors: Motavkin A.V., Pokrovskii E.M.,
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Elibrary: https://elibrary.ru/item.asp?id=43791338
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It was shown that depending on the phase state of a polymer guest, poly(propylene oxide), two kinds of inclusion complexes with β-cyclodextrin may be prepared. In a homogeneous solution, complex A is obtained, while in the case of emulsion, complex B is synthesized. The compositions of both complexes are independent of the molecular mass of the polymer and correspond to a molar ratio of β-cyclodextrin: polypropylene oxide) repeat unit: H20 =1:2 :n. The number of water molecules u is 6 and 2 for complexes A and B, respectively. According to X-ray data, complex A has a crystalline structure composed of monoclinic crystals. Complex B forms a columnar mesophase with the hexagonal arrangement of cyclodextrin columns in the base plane. It was discovered that the studied complexes are capable of mutual transitions: upon the annealing of A complexes, a crystal-mesomorphic structure transition takes place simultaneously with the loss of water. The addition of water to the mesomorphic complex B and the subsequent prolonged stirring of a suspension at ~5°C are accompanied by the formation of a monoclinic crystalline structure.
Authors: Popova E.I., Topchieva I.N., Zhavoronkova E.V., Panova I.G., Matukhina E.V., Gerasimov V.I.,
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Elibrary: https://elibrary.ru/item.asp?id=43791339
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The IR and Raman spectra of poly(dialkylaminophosphazene)s (PDAAPs) [-Ρ(ΝΗΟmΗ2m+)2=Ν-]n with m = 1-7 were measured in the temperature range -100 to +20°C and at room temperature, respectively. Vibrational modes in the spectra of PDAAPs were assigned with reference to the previously obtained spectral data on poly(dialkoxyphosphazene)s. The absence of conformational transitions due to the rotation about P-N and C-N bonds in the side groups was demonstrated for all of the poly(dialkylaminophosphazene)s examined. Temperature-induced variations in the IR spectra of PDAAPs with m > 4 are due to the gauche-trans transitions resulting from internal rotation about C-C bonds in the side groups, as well as to the changes in the backbone structure. No changes in the main-chain structure were observed for PDAAPs with m< 4 because of hydrogen bonds formed by NH groups.
Authors: Komarova L.I., Mukhametova N.I., Tur D.R., Papkov V.S., Lokshin B.V.,
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Elibrary: https://elibrary.ru/item.asp?id=43791340
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The thermodynamic functions of mixing of starch with carboxymethyl cellulose sodium in films obtained from aqueous solutions at different temperatures were studied. For compositions with different starch contents, the enthalpies of dissolution in water and the sorption isotherms of water vapor were determined by the calorimetric and sorption methods. The enthalpies, Gibbs energies, and entropies of mixing of starch with carboxymethyl cellulose sodium in the entire range of compositions were calculated from the thermodynamic cycle. It was shown that all the thermodynamic functions are negative, which is indicative of the thermodynamic compatibility the components, their strong intermolecular interactions, and high ordering in the course of mixing. The affinity of the components to each other, which is due largely to the entropy factor, increases with the temperature of film formation.
Authors: Suvorova A.I., Safronov A.P., Mel'nikova O.A.,
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Elibrary: https://elibrary.ru/item.asp?id=43791341
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Hyperbranched perfluorinated poly(phenylenepolygermanes) intramolecularly impregnated by lanthanide fluorides were synthesized. The polycondensation of (C6F5)3GeH activated by La, Eu, Gd, and Yb compounds leads to the encapsulation of the formed metal fluorides in the cavities of dendritic macromolecules. Polymers containing up to 12% metal fluoride were prepared by the reactions of metal naphthalene complexes C10H8Ln(THF)3 (Ln = Eu, Yb). The reactions of (C6F5)3GeH with isopropoxides (iso-C3H70)3Ln, acetylacet-onates Ln(AcAc)3 (Ln = La, Gd), and europium phenylacetylenide (PhC=C)2Eu yield polymers containing no less than 2% LnF3. The reaction products were studied by gel permeation chromatography, IR and 19F NMR spectroscopy, scanning probe microscopy, and photoluminescence.
Authors: Bochkarev M.N., Brezhneva I.I., Katkova M.A., Semchikov Yu. D., Maksimov G.A., Gushchina Yu. Yu., Vitukhnovskii A.G., Lepnev L.S.,
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Elibrary: https://elibrary.ru/item.asp?id=43791342