The synthesis and gas-transport properties of new metathesis-type polynorbornenes bearing fluoroorganic side groups are reported. The necessary monomers, fluorosubstituted exo-norbornene derivatives ...(exo-tricyclononenes), were obtained using one-step method based on stereo- and regioselective 2 + 2+2-cycloaddition of quadricyclane and fluoroalkenes. A set of high molecular weight polymers with different side groups were prepared from the synthesized F-substituted exo-tricyclononenes over the 1-st generation Grubbs catalyst. Permeability and diffusion coefficients of various gases (He, H2, O2, N2, CO2, CH4) in these poly-exo-tricyclononenes were determined for the first time and new relationships between polymer structure and gas permeability were established. Metathesis poly-exo-tricyclononene bearing four CF3-groups in each monomer unit displayed the highest gas permeability for the tested gases among metathesis polynorbornenes with F-organic substituents reported so far.
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•Novel highly reactive fluoro-containing exo-tricyclononenes were synthesized via 2 + 2+2-cycloaddition reaction.•A group of new metathesis polytricyclononenes bearing side fluoroorganic-substituents was prepared.•The obtained polymers possessed both the chemical and thermal stability.•The synthesized metathesis polytricyclononenes with fluorooganic-substituents exhibited the improved gas permeability.•New structure-property relationships for polynorbornenes were established.
Addition polymerization of cycloalkenes (cyclopentene, cyclopentadiene, cyclooctene, cyclooctadiene) in the presence of a new type of catalytic systems—Pd(0) complexes activated with arendiazonium ...salts—was studied. It was shown that cyclopentene, cyclooctene, and cyclooctadiene are not active in polymerization with these catalytic systems, while cyclopentadiene is actively involved in polymerization. The polycyclopentadiene structure was confirmed by
1
H NMR spectroscopy. The molecular weight parameters and microstructure of the polymer were determined.
The vertical turbulent dust aerosol (DA) and heat fluxes are determined on the basis of measured fluctuations of the components of the wind speed, air temperature, and concentration of aerosol ...particles on a desertified territory of Astrakhan oblast during intermittent DA emission. The temporal variability of the horizontal and vertical components of the wind speed, air temperature, and concentration of aerosol particles is characterized using spectral analysis. It is shown that the intermittent DA emission is caused by low-frequency convective-related variations in the horizontal component of wind speed if the threshold saltation speed is exceeded. The significant differences in the spatiotemporal variability of vertical heat and DA flux are revealed. The 30-min average values of heat (90‒158 W/m
2
) and DA (7.2‒27.5 cm
–2
cm
–1
) fluxes, as well as the rates of heat (14‒21 cm/s) and DA (10‒16 cm/s) removal, are calculated.
Reversible addition–fragmentation chain-transfer radical copolymerization of ethylene with vinyl acetate in the presence of azobis(isobutyronitrile) and xanthate as a chain-transfer agent was ...studied. Products containing 12–42 mol % vinyl acetate units were prepared under varied reaction conditions. The glass transition points and degradation temperatures of the polymers were determined. The rheological properties of ethylene–vinyl acetate copolymers were studied in detail. The effect of additions of the copolymers synthesized on the rheological characteristics of diesel fuel was evaluated. The ethylene–vinyl acetate copolymers synthesized reduce the limiting filterability temperature of the diesel fuel.
Vertical turbulent and convective fluxes and corresponding velocities of the dust aerosol particle uplift under conditions of quasiperiodic emission have been determined by the measurements of the ...dust aerosol particle concentrations and the turbulent fluctuations of the wind speed components in a desertified area in the Astrakhan region. It is shown that convective fluxes are caused by the combined action of both regular upward motions (updrafts) in the convective coherent structure of the atmospheric boundary layer and turbulent diffusion. In the surface layer of the atmosphere at heights from 0.3 to 6.0 m, the vertical profiles of the dust aerosol concentration are approximated by power functions. It is demonstrated that the vertical turbulent and convective fluxes of dust aerosol can be estimated by the gradient method using the scales of turbulent and convective vertical motions in the atmospheric boundary layer.
The microstructure of low-molecular-mass ethylene–vinyl acetate copolymers was studied by
1
Н and
13
С NMR spectroscopy. The vinyl acetate mole fraction, chain branching, and mean lengths of ethylene ...and vinyl acetate blocks were determined. The thermal properties of ethylene–vinyl acetate copolymers were studied by differential scanning calorimetry and thermogravimetric analysis, and the crystalline characteristics, by X-ray diffraction analysis. The degree of crystallinity of the copolymer decreases with an increase in the fraction of the polar comonomer. Rheological studies show that ethylene–vinyl acetate copolymers at room temperature tend to microphase segregation and form a microphase structural network.
The review article is devoted to high-temperature borosilicate molybdenum alloys reinforced with titanium carbides MoSiBTiC. The article discusses phase diagrams, microstructure, production methods, ...mechanical properties, resistance to oxidation of these alloys, and protective coatings. It is shown that the long-term strength of MoSiBTiC alloys is superior at high temperatures to nickel heat-resistant alloys (NHRA) of the latest generations. Borosilicate molybdenum alloys MoSiBTiC can replace nickel heat-resistant alloys in many engineering fields, including in the production of cast parts for the hot section of aircraft gas turbine engines.
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Using the commercial derivative of norbornene—5-ethylidene-2-norbornene—a series of three isomeric homopolymers with different structure of the backbone is synthesized, and the effect of the chain ...structure on the gas-transport behavior of polynorbornenes is studied. The gas-transport characteristics of the polymers are presented together with data on the conformation properties of molecules of addition and metathesis polynorbornenes. The effect of the structure of side substituents on the equilibrium rigidity of addition polynorbornenes is confirmed by the example of poly(5-ethylidene-2-norbornene) and poly(5-vinyl-2-norbornene).
Previously undescribed norbornene monomer 3,3,4-trifluoro-4-perfluorohexyltricyclononene-7 is synthesized by the 2+2+2 cycloaddition reaction. The monomer is involved in the ring-opening ...polymerization metathesis in the presence of the first-generation Grubbs catalyst to give rise to the amorphous, glassy unsaturated polymer. The gas-transport properties of the metathesis polymer is studied, the gas permeability and diffusion coefficients for a wide range of gases (He, H
2
, O
2
, N
2
, CO
2
, CH
4
) are determined, and the solubility coefficients of gases in this polymer are calculated.
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