Influence of the Solvent on the Formation of CNR/BNR Polymer Blends

Structural dynamic analysis combining IR spectroscopy, DSC, and EPR spectroscopy is applied to studying films based on chlorinated natural rubber (CNR), butadiene nitrile rubber (BNR), and blends thereof. The influence of various solvents, such as methyl ethyl ketone (MEK), ethyl acetate (EA), methyl acetate (MA), and acetone (A), on the structure and molecular dynamics (τ) of CNR/BNR polymer films is examined. The strongest changes in the molecular mobility (τ) and the glass transition temperature (T_gt) relative to those of the starting materials are observed for the 50: 50% CNR/BNR blends prepared using all the solvents (except for acetone, the maximum values of τ for which is observed at a ratio of CNR: BNR = 80: 20%), which can be explained by the inversion of phases in the blends. Annealing at 140°С causes an increase in the correlation time of the probe, and, consequently, a decrease in the molecular mobility, which is due to the intermolecular crosslinking of the components.     

Determination of the Ch acidity of certain ethyne ethers by polarographic reduction of their mercury derivatives

Conclusions New mercury derivatives of the ethyne ethers and sulfides have been prepared and their CH acidities determined by the polarographic reduction method.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1744–1747, August, 1981.     

Solubility and volume behavior of solutions of hydrogen and carbon monoxide in 2-methylbutanal

The compositions and molar volumes of the liquid phase in the hydrogen-2-methylbutanal and carbon monoxide-2-methylbutanal systems on the liquid-gas boundary curve were investigated. The molar volumes of 2-methylbutanal were determined. The data were treated by means of correlation equations, and the Henry coefficients and the heats of solution of hydrogen and carbon monoxide in 2-methylbutanal were calculated.Lenneftekhim Scientific Production Society. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 2, pp. 241–244, March–April, 1991. Original article submitted June 1, 1987.     

Pointwise estimate of the solution to a quasilinear elliptic problem in a domain with a thin cavity

We derive a pointwise estimate of the solution to Dirichlet's problem for a quasilinear second-order elliptic equation in a domain whose bounded compliment is contained in a small neighborhood of a set {x Rⁿ: ¦x¦ 1/2, x₁=...=x_s=0}.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 44, No. 10, pp. 1417–1432, October, 1992.     

Cyclization of N-alkylazinium cations with bifunctional nucleophiles. 14. Reaction of quinoxalinium salts with mono- and N,N′-disubstituted amidines

Monosubstituted benzamidines undergo cyclization with quinoxalinum salts to give 1,2-disubstituted 3a,4,9,9a-tetrahydroimidazo[4,5-b]quinoxalines. The participation in similar cyclizations of N,N-disubstituted amidines with a CH-active group in the a position leads to 3a,4,9,9a-tetrahydropyrrolo[2,3-b]quinoxalines.See [1] for Communication 13.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 390–395, March, 1985.     

Heat-conducting adhesives based on modified epoxy resins

Main characteristics of heat-conducting adhesive materials used to withdraw heat from warming elements of devices and the joints of electrotechnical equipment are presented. The developed materials, i.e., TsMK-TP adhesive pastes and TPK convenient for application adhesives, are cold-curing compositions based on epoxy-diane resins modified with Laproxide products. They have heat conductivity coefficients of no less than 1.8 W/(m K), are workable in the temperature range of −196 to 150°C (up to 200°C for a short period of time), and do not contaminate optical elements due to minimal gas release under exposure to vacuum and increased temperatures.     

Influence of the solvent on the segmental dynamics and structure in mixed compositions of polyurethane and styrene-acrylonitrile copolymer

The effect of the tetrahydrofuran (THF), methyl ethyl ketone (MEK), ethyl acetate (EA), and acetone (A) solvents on the structure and segmental dynamics of polyurethane (PU)-(styrene-acrylonitrile) (SAN) mixed compositions are studied by spin-probe EPR spectroscopy, differential scanning calorimetry, and infrared spectroscopy. The molecular mobility τ, the degree of crystallinity χ, the modulus of elasticity E alter only slightly in passing from 100% PU to a 50% PU-50% SAN, but the structural and dynamic properties change abruptly at a high SAN content in the composition, regardless of the type of solvent. The values of τ, χ, and elastic modulus for the mixed compositions increases depending on the type of solvent in the following sequence: THF, MEK, EA, A, which can be explained by the thermodynamic affinity between the solvent and solute. It is also shown that, with growing content of SAN in the composition, the number of intermolecular hydrogen bonds between nitrile and urethane groups (3344-cm^?1 band) increases.     

Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.     

Crystal and molecular structures of (3Z)-(±)-4-(2′-hydroxypropyl)amino-and (3Z)-4-(2′-hydroxyethyl)amino-pent-3-en-2-ones

An X-ray study of (3Z)-(±)-4-(2′-hydroxypropyl)amino-and (3Z)-4-(2′-hydroxyethyl)amino-pent-3-en-2-ones is reported. The bond lengths inside the H ring are equalized due to the classical N-H...O hydrogen bond between the carbonyl oxygen and the amino group. In the 4-(2′-hydroxyethyl)amino-pent-3-en-2-one crystal, due to the classical N-H...O bonds, infinite zigzag chains are formed along the 0b axis and arranged into a layered structure due to the weak C-H...O interactions. In (±)-4-(2′-hydroxypropyl)aminopent-3-en-2-one crystal, however, centrosymmetric dimers are formed, which are then linked by weak C-H...O intermolecular interactions to form a layered structure along the a0b plane.