卷 51, 编号 3 (2017)

The molecular–topological structure of a copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether) before and after γ-irradiation has been studied for the first time. The pseudo-network structure of the copolymer contains an amorphous block and the crystalline segments of macromolecules serve as branching points. After γ-irradiation to a dose of 15 to 2380 kGy, polyassociative cluster-type entities have appeared in the initial copolymer in place of the crystalline branching points with simultaneous structure amorphization and a decrease in the onset temperature of molecular flow.

On the basis of analysis of published data on the reaction efficiency of various polymer materials and graphite in their interaction with fast oxygen atoms (energy of about 4.5 eV) as obtained in flight tests of materials in low-Earth orbits of the International Space Station and ground tests, probability P_r of chemical oxidation reactions accompanied by ablation has been evaluated. Estimates have been made for 33 polymers consisting of carbon, hydrogen, oxygen, and nitrogen and graphite for two extreme cases when the carboncontaining oxidation products are either CO or CO₂ alone. The average probability values found are P_r(CO)(av) = 0.184 and P_r(CO₂)(av) = 0.317. The probability values range from P_r(CO) = 0.604 and P_r(CO₂) = 0.963 for allyl diglycol carbonate to P_r(CO) = 0.038 and P_r(CO₂) = 0.075 for pyrolytic graphite.

The spectral–luminescent, photophysical, and photochemical properties of dichloro-, dibromo-, and diiodo-derivatives of boron dipyrromethenate (BODIPY) have been studied, as well as the feasibility of generating singlet oxygen (¹O₂) via its photosensitization by the dihalogenated derivatives of BF₂ dipyrromethene in solutions. Quantum yields of singlet oxygen have been determined using 1,3-diphenylisobenzofuran as the ¹O₂ trap. The lowest fluorescence quantum yields have been shown to correspond to the maximum yields of singlet oxygen. It has been found that the best ¹O₂ photosensitizer among the three test dihalotetraphenylaza- BODIPY is dibromotetraphenylaza-BODIPY, which in addition possesses the highest photostability. Diiodotetramethyl-BODIPY results in the singlet oxygen yield close to unity, but it has significantly lower photostability. The yield of singlet oxygen is affected by the solvent. Dibromtetraphenylaza-BODIPY and diiodotetramethyl-BODIPY may find use as a medium in photodynamic therapy and photocatalysis of oxidation reactions.

Using absorption, luminescence, ¹H NMR, and laser kinetic spectroscopies, the photophysical processes and photochemical reactions of 4-[(E)-2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxacyclooctadecin-18-yl)vinyl]-1-ethylpyridinium perchlorate and its complexes with lithium, sodium, potassium, calcium, barium, silver, and lead perchlorates in MeCN have been studied. The styryl dye and its complexes with metal cations are capable of emitting normal (prompt) and delayed fluorescence and enter into the trans–cis photoisomerization reaction. The dye molecules in the triplet state participate in the processes of degradation of electronic excitation energy. Triplet–triplet absorption is observed only in the presence of lead cations with a maximum at 470 nm and the deactivation rate constant of the triplet state k = 2.5 × 10⁴ s^–1 in a deoxygenated solution.

Photochemical properties of bis(styrylbenzoquinoline) dyads in which two styrylbenzoquinoline (SBQ) moieties are bridged by an o-xylylene group linked to their styryl groups via oxy- and carboxy-functional groups have been studied. Two competitive reactions, photoisomerization of the SBQ moieties and stereoselective [2 + 2] photocycloaddition (PCA) to give tetrasubstituted cyclobutane, occur under irradiation. It is assumed that PCA occurs with participation of an intramolecular excimer, in which the photochemical process of dimerization to cyclobutane dominates over the photophysical process of fluorescence, because the emission band of the excimer is not observed in an explicit form in the fluorescence spectra of dyads.

Photostimulated oxidation of water by potassium persulfate in the presence of photosensitizer bpy₃RuCl₂ ∙ 6H₂O and ruthenium catalyst Li₁₀[{Ru₄(μ-O)₄(μ-OH)₂(H₂O)₄} ∙ (γ-SiW₁₀O₃₆)₂] ∙ 10H₂O has been studied. It has been shown that the quantum yield of O₂ (0.29) is much higher than the quantum yield in a similar photocatalytic system with rubidium countercations (0.09).

The possibility of obtaining nanosized nickel powder by simultaneous dc electrolysis and high-voltage spark discharge has been explored. The powder has been prepared from a nickel sulfate-containing electrolyte using soluble nickel anodes at a cathodic current density in the range of 11000–19000 A/m², a voltage on the spark gap of 12–16 kV, and a pulse repetition frequency of 0.5 Hz. The effect of various factors on the synthesis of the powder has been studied and the optimum conditions for its preparation have been found using mathematical experiment design. The size distribution of particles has been determined with a particle size analyzer. The BET specific surface area of the powder has been measured to be 11.7 ± 2.1 m²/g.

Changes in surface properties and composition of the surface layer of polycarbonate of the Lexan LS2 and Lexan 8010 brands after treatment in the positive column of glow-discharge oxygen plasma have been studied. The amount of the polymer loaded for processing has been shown to affect the kinetics of etching and modifying the polycarbonate surface. It has been found that an increase in the amount of the polymer in the plasma reduces its etching rate and also affects the electrical parameters of plasma, which in turn can cause a change in the flux of active species onto the polymer surface and, consequently, a change in the rate of plasma-initiated heterogeneous processes.