Russian Journal of Applied Chemistry最新文献

Vanadium oxide nanocoatings of various thicknesses were synthesized by the atomic layer deposition (ALD) through cyclic alternating treatment of polycrystalline α-Al₂O₃ plates with vapors of vanadium(V) oxochloride and water. Diffuse reflectance spectroscopy, demonstrated that, depending on the number of treatment cycles, complexes of various structures are generated on the surface, containing distorted aluminovanadate structures, layers with tetrahedral vanadium coordination, and polyhedra, in which the vanadium atom environment coordinated with oxygen is similar to the state in crystalline V₂O₅. Based on the results of studies using an atomic force microscope, it was found that depending on the thickness of the growing layer, the surface morphology and the degree of its overlap change. After 600 cycles of treatment with vapors of vanadium(V) oxochloride and water, a coating is formed that completely covers the surface of the original substrate. A composition based on polycrystalline α-Al₂O₃ with a functional vanadium oxide layer exhibits sensor properties in relation to such components of the gas environment as NO₂, CO, NH₃, H₂S, H₂.

Separation of CO₂/CH₄ and CO₂/N₂ mixtures containing from 20 to 50% CO₂ on membranes based on polytricyclononenes with tri(n-alkoxy)silyl groups containing substituents with alkyl fragments of different lengths (one to four carbon atoms), prepared by vinyl-addition polymerization, was studied. The separation selectivity for these mixtures is close to the corresponding ideal selectivity. The gas transport characteristics slightly depend on the pressure of the gas feed flow. The best results are obtained for the polymer with methyl groups in pendant substituents. The parameters of this polymer are located above the 2015 upper bound in the Robeson diagram for CO₂/CH₄ gas mixtures.

Local Young’s modulus values on the surface of Lestosil SM block copolymer films with different content of the modifying filler were determined by contact force spectroscopy with a Solver P47 scanning probe microscope installation.

A procedure was developed for preparing block synthons by the reaction of 2,4-pentanedione, 1,2-ethanedithiol, and aromatic aldehydes in the presence of an organic catalyst (triethylamine, piperidine, diazabicycloundecene, morpholine) to construct heterocycles derived from bis(arylmethylsulfanyl diketones). Among the bis(sulfanyl diketones) prepared, the compounds containing p-methoxyphenyl and thienyl substituents in the methinesulfanyl moiety showed the highest fungicidal activity toward phytopathogenic fungi Bipolaris sorokiniana, Fusarium oxysporum, and Rhizoctonia solani.

The relative humidity and saturated water vapor pressure resulted from the reversible equilibrium dissociation of crystalline NaBH₄·2H₂O in the temperature range 0–36°C were determined. Based on the data obtained for NaBH₄·2H₂O, the equilibrium water vapor pressure as a function of temperature ln P = –6567.1T^–1 + 23.863, enthalpy ∆Н₀ = 54 ± 0.8 kJ mol^–1 and entropy ∆S₀ =198 ± 2 J mol^–1 K^–1 of NaBH₄·2H₂O dissociation into NaBH₄ and H₂O, standard enthalpy ∆H°= –783 kJ mol^–1 and entropy ∆S° = 281 J mol^–1 K^–1 of formation of NaBH₄·2H₂O were calculated. An equation was derived for the humidity vs. temperature, which determines the regions of NaBH₄·2H₂O formation or its dissociation Rh = 0.334t + 17.5. It was shown that the pressure of saturated water vapor over a concentrated NaBH₄ solution (30 wt %) at temperatures up to 45°C has higher values compared to NaBH₄·2H₂O samples synthesized by two different methods.

The features of chlorosulfonated polyethylene thermolysis were studied and it was found that free radicals formed after the simultaneous homolytic cleavage of carbon–sulfur and sulfur–chlorine bonds not only react with each other (recombination or disproportionation), but also abstract a hydrogen atom from the macromolecule of polyethylene or ethylene–propylene rubber, providing crosslinking of macromolecules, accompanied by an increase in the strength properties of composites based thereon.

Surface modification of carbon fiber with 1,1-dihydroperoxycyclohexane (DHPC) before application of SiO₂ barrier coating was studied. IR spectroscopy showed presence of the COOH carboxyl groups on the surface of modified carbon fibers. The modified surface has less hydrophobicity due to the presence of polar groups, which contribute to a change in the wettability of the fiber by the sol–gel solution and the adhesion of the oxide coating to the fiber surface. The quality and thickness of the oxide coatings were assessed by scanning electron microscopy. The use of DHPC leads to oxidation of the carbon fiber, making surface longitudinal stripes deeper. To determine the effect of DHPC modification on the properties of the fiber surface, a SiO₂ coating was applied by immersion in a tetraethoxysilane sol. DHPC modification leads to the formation of a uniform SiO₂ coating on the fiber surface. After the heat treatment, the coating thickness on the DHPC–modified fibers is 130 ± 30 nm. Analysis of the IR spectra showed that the addition of DHPC to the sol leads to an increase in the intensity of the Si–O–Si, Si–OH, and OH absorption bands, which are characteristic of the hydrolysis and polycondensation products of tetraethoxysilane. In the wavenumber range of 400–1200 cm^–1, the Si–O–Si fragments form, which is confirmed by the presence of bands of Si–O– deformation bond at ν = 881 and 442 cm^–1. The introduction of DHPC into the sol promotes the formation of a uniform coating on the carbon fibers. The coating thickness on the initial fibers reaches 410±100 nm at room temperature, decreasing to 190±60 nm after heating. The fiber and sol modification contribute to formation of a uniform coating with a thickness of 200 ± 70 nm and 130 ± 30 nm before and after the heating, respectively. DHPC modification of the fiber surface and tetraethoxysilane sol promotes the formation of continuous, uniform, and quality SiO₂ coatings on the surface of carbon fibers.

p-Aminophenylcyclopropylmethyl methacrylate monomer was prepared, and its free-radical copolymerization with methyl methacrylate was performed. The monomer and copolymer were characterized by IR and NMR spectroscopy. The relative activity constants of the monomer were determined, and the monomer activity and polarity were calculated by the Alfrey–Price method. The copolymerization constant of p-aminophenylcyclopropylmethyl methacrylate exceeds that of methyl methacrylate; therefore, the copolymer is enriched in units of specifically this comonomer. The copolymers based on p-aminophenylcyclopropylmethyl methacrylate exhibit high biological activity toward Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and toward Candida albicans fungi.

The processes of self-organization of a cysteine–silver solution and the effect of heating and ultraviolet radiation on the self- organization and formation of silver nanoparticles were studied using UV spectroscopy. The key factor influencing the formation of silver nanoparticles is UV radiation. Heating the cysteine–silver solution to 60°C does not affect the formation of silver nanoparticles.

The complexation of cefotaxime with an anionic polysaccharide, sodium alginate, in aqueous solutions with different pH values was studied by conductometry and by UV and IR spectroscopy. The compositions and stability constants of the complexes were determined. At pH 2.0, 5.6, and 7.2, the composition of the complex of cefotaxime with alginate corresponds to the [cefotaxime] : [alginate] molar ratio of 4.0 : 1.0, 2.3 : 1.0, and 1.0 : 1.0, respectively. The cefotaxime–alginate complex is most stable in strongly acidic media.