Kinetics of Gaseous Product Formation in the Surface Treatment of Polypropylene with Nitrogen–Oxygen Plasmas

The results of measurements on the composition and the formation rates of gaseous products in the surface treatment action of polypropylene with a low-temperature dc discharge plasma in a nitrogen–oxygen mixture are reported. The amount of oxygen in the mixture was varied within 0–100%. It was found that almost stoichiometric plasma-induced oxidative degradation occurred in an oxygen plasma, whereas the buildup of oxygen-containing functional groups on the surface took place in a mixed nitrogen–oxygen plasma at a nitrogen content of 10–60%.     

Formation of the layering boundary in the water–benzene–perfluorobenzene system

The dynamics of the interface between liquid phases in the water–benzene–perfluorobenzene system was studied in a natural experiment. The interfacial tension was found to depend on the density of the organic layer. The range of interfacial tensions in which inversion of the organic and aqueous phases takes place was determined, and the working range of a separating flask as an element of the separation scheme for the mixture was revealed.     

Induced Collapse in the Formation of Alternating Langmuir–Blodgett Films

Two compounds whose molecules have large dipole moments, strereoregular perfluorinated alkylmethacrylate-co-methacrylic acid (A) and p-octadecylaminoazobenzene-p"-sulfamide (B), were used to assemble Langmuir–Blodgett polar films by the alternating method to achieve high polarization. According to estimates, the dipole moment of the dimeric unit of copolymer A is equal to about 4 D, the dipole moment of compound B, to 12 D. Unusually high (several units) transfer ratio was observed for the monolayer B when preparing the structures of (AB) _n type. The monolayers were stable during their formation process. Upon the pause of a substrate when passing through the monolayer B, the monolayer area remained strictly constant. According to the model proposed, the monolayer looses its stability and locally collapses in the meniscus zone at the contact line of the monolayer B and substrate due to an increase in the electrostatic repulsion between the dipoles of molecules B. The validity of this model is confirmed by the data of small-angle X-ray diffraction and atomic force microscopy for various alternating Langmuir–Blodgett films.     

The Role of Surfactants in the Formation of Highly Dispersed Iron–Zirconium Oxide Composites with Uniform Pores

The effects of the nature and concentration of surfactants and the preparation conditions on the genesis of iron–zirconium composites with a [Fe³⁺]/[Zr⁴⁺] ratio of 0.123 were studied. The effect of surfactants on the physicochemical properties of precipitates is determined by the conditions of synthesis. The amount of surfactants retained by the precipitate at pH 3 is about an order of magnitude greater than at pH 9. The thermolysis of samples synthesized at acidic pH is accompanied by the dehydration and dehydroxylation of iron–zirconium composites as well as by the decomposition and destruction of surfactants. In the latter processes, compounds or their fragments capable of reducing some phases are removed in a stepped-up manner. The specific surface area of oxide systems formed in this way is at most 100–150 m²/g. In the pH range corresponding to the complete precipitation of the components, highly dispersed single-phase and uniformly porous composites are formed. The choice of a surfactant, its fraction, and preparation conditions enables the preparation of oxides with specific surface areas of 100–400 m²/g. The average pore diameter of the samples ranges from 3.0 to 27.0 nm, and the total pore volume ranges from 0.20 to 0.38 cm³/g.     

Formation of calcium in the products of iron oxide–aluminum thermite combustion in air

The composition of condensed products resulting from the combustion of thermite mixtures (Al + Fe₂O₃) in air is studied by precise methods. It is shown that during combustion, calcium is formed and stabilized in amounts of maximal 0.55 wt %, while is missing from reactants of 99.7 wt % purity. To explain this, it is hypothesized that a low-energy nuclear reaction takes place alongside the reactions of aluminum oxidation and nitridation, resulting in the formation of calcium (Kervran–Bolotov reaction).     

Manifestation of the Even–Odd Effect in the Spectral Properties of Solvated Electron and in the Probability of Positronium Formation in Alcohols

A change in the energy E _max of the solvated electron, which corresponds to the maximum intensity of its optical absorption spectrum in the homologous series of alcohols seems to be alternating in character. The effect is retained upon elevation of pressure up to 2 kbar but disappears in alcohols frozen at 77 K. Probably, the effect also holds for amines. The alternating character of variation is also observed for the intensity Y ₁ of the narrow components of the angular spectrum of -photons generated upon positron annihilation in alcohols and normal alkanes. The nature of alternation of E _max is associated with the mutual elimination of electric fields induced by the dipole moments of two neighboring CH₂ groups in each solvent molecule, including also the molecules forming the solvation shell of an excess electron. That fact that the E _max value correlates to Y ₁ led to the conclusion that Y ₁, rather than the intensity I ₃ of the long-lived component of the annihilation time spectrum generally used for the purpose, more adequately characterizes the positronium formation probability.     

Direct Mechanism of the First Carbon–Carbon Bond Formation in the Methanol-to-Hydrocarbons Process

In the past two decades, the reaction mechanism of C−C bond formation from either methanol or dimethyl ether (DME) in the methanol-to-hydrocarbons (MTH) process has been a highly controversial issue. Described here is the first observation of a surface methyleneoxy analogue, originating from the surface-activated DME, by in situ solid-state NMR spectroscopy, a species crucial to the first C−C bond formation in the MTH process. New insights into the first C−C bond formation were provided, thus suggesting DME/methanol activation and direct C−C bond formation by an interesting synergetic mechanism, involving C−H bond breakage and C−C bond coupling during the initial methanol reaction within the chemical environment of the zeolite catalyst.     

Charge Formation on the Surface of a Laminated Polyimide–Fluoroplastic Film by Direct-Current Discharge Treatment

The effect of a direct-current discharge on the tetrafluoroethylene–hexafluoropropylene copolymer (FP) layer of laminated polyimide–fluorocarbon polymer films (including the commercial film PMF-351) placed in the cathode fall was studied. The magnitude of the negative charge induced in the films was shown to be independent of the film thickness. A thermostimulated relaxation curve for the PMF-351 film exhibited two peaks, one at 484 K due to relaxation of the negative charge in the bulk of the FP layer and the other at 417 K characteristic of negative charge relaxation in the polyimide layer. The results are explained by detrapping of electrons by plasma UV radiation that is not absorbable by the FP layer.     

Geometrical Changes and Their Energies in the Formation of Donor–Acceptor Complexes

We have mapped the energy demands of the geometrical changes in donor–acceptor complexes BH₃NH₃ and AlCl₃NH₃ and in the course of their formation from their monomers. We have varied the individual geometrical parameters systematically and performed ab initio quantum chemical calculations for these structures. We investigated the energy requirements to change bond lengths and bond angles in both the monomers and complexes and the angles of torsion in the complexes. The changes of bond lengths require more energy in the monomers than in the complexes. The energies to change the acceptor bond angles in the monomers are markedly higher than in the complexes. The changes in the geometrical parameters during the complexation process are more moderate in donors than in acceptors, in agreement with prior experimental observations. The geometry versus energy variations related to the process of complexation are in agreement with the notion of relative rigidity of the donor parts and the more compliant nature of the acceptor parts as well as with the notion of competing effects in the structures of the complexes.     

Formation of Diazepam–Lanthanides(III) Complexes in the 50–50 Volume % Ethanol–Water Solvent System and Study of the Effect of Temperature on the Complex Formation Constants

Diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) is an important derivative of the 1,4-benzodiazepine compound commercially distributed as Valium. The complex formation constants of diazepam with some light lanthanide(III) metal ions have been studied by potentiometric measurements. All titrations were performed in 50–50% (volume/volume) ethanol–water solvent mixtures at constant ionic strength (0.10 mol⋅dm⁻³). The ionic strength was maintained by using sodium perchlorate. The complex formation constants were determined at 25.00, 35.00 and 45.00 °C. With increasing temperature, a decrease was observed in the protonation constant (pK) of diazepam.     

Efficient Covalent Bond Formation in Gas-Phase Peptide–Peptide Ion Complexes with the Photoleucine Stapler

Noncovalent complexes of hydrophobic peptides GLLLG and GLLLK with photoleucine (L*) tagged peptides G(L* _n L _m )K (n = 1,3, m = 2,0) were generated as singly charged ions in the gas phase and probed by photodissociation at 355 nm. Carbene intermediates produced by photodissociative loss of N₂ from the L* diazirine rings underwent insertion into X?H bonds of the target peptide moiety, forming covalent adducts with yields reaching 30%. Gas-phase sequencing of the covalent adducts revealed preferred bond formation at the C-terminal residue of the target peptide. Site-selective carbene insertion was achieved by placing the L* residue in different positions along the photopeptide chain, and the residues in the target peptide undergoing carbene insertion were identified by gas-phase ion sequencing that was aided by specific ¹³C labeling. Density functional theory calculations indicated that noncovalent binding to GL*L*L*K resulted in substantial changes of the (GLLLK + H)⁺ ground state conformation. The peptide moieties in [GL*L*LK + GLLLK + H]⁺ ion complexes were held together by hydrogen bonds, whereas dispersion interactions of the nonpolar groups were only secondary in ground-state 0 K structures. Born-Oppenheimer molecular dynamics for 100 ps trajectories of several different conformers at the 310 K laboratory temperature showed that noncovalent complexes developed multiple, residue-specific contacts between the diazirine carbons and GLLLK residues. The calculations pointed to the substantial fluidity of the nonpolar side chains in the complexes. Diazirine photochemistry in combination with Born-Oppenheimer molecular dynamics is a promising tool for investigations of peptide–peptide ion interactions in the gas phase.

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Formation of organic peroxides in the photooxidation of CH_4

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Specific Features of Radical Formation in the Trialkylborane–Oxygen System and the Gluing Mechanism of Acrylate Composites

Russian Journal of Applied Chemistry - Fundamental study of how radicals are generated, with involvement of trialkylboranes combined with oxygen and organoelement peroxides, was carried out. It was...     

Formation of acridones by ethylene extrusion in the reaction of arynes with β-lactams and dihydroquinolinones

N-Unsubstituted β-lactams react with a molecule of aryne by insertion into the amide bond to form a 2,3-dihydroquinolin-4-one, which subsequently reacts with another molecule of aryne to form an acridone by extrusion of a molecule of ethylene. 2,3-Dihydroquinolin-4-ones react under the same reaction conditions to afford identical results. This is the first example of ethylene extrusion in aryne chemistry.     

Formation of solid solutions in the CdSe–PbSe system under the action of high pressures and temperatures

A method was proposed for producing solid solutions in the CdSe–PbSe systems, which is based on heat and high pressure treatment. X-ray powder diffraction analysis showed the formation of substitutional solid solutions Cd_xPb_1–xSe with the NaCl structure, which contained 20, 40, 60, and 80 mol % cadmium selenide. The solid solutions were characterized by scanning electron microscopy, impedance spectroscopy, gas pycnometry, and Raman spectroscopy.     

Selective Formation of Polyaniline Confined in the Nanopores of a Metal–Organic Framework for Supercapacitors

In this study, a strategy that can result in the polyaniline (PANI) solely confined within the nanopores of a metal–organic framework (MOF) without forming obvious bulk PANI between MOF crystals is developed. A water-stable zirconium-based MOF, UiO-66-NH₂, is selected as the MOF material. The polymerization of aniline is initiated in the acidic suspension of UiO-66-NH₂ nanocrystals in the presence of excess poly(sodium 4-styrenesulfonate) (PSS). Since the pore size of UiO-66-NH₂ is too small to enable the insertion of the bulky PSS, the quick formation of pore-confined solid PANI and the slower formation of well dispersed PANI:PSS occur within the MOF crystals and in the bulk solution, respectively. By taking advantage of the resulting homogeneous PANI:PSS polymer solution, the bulk PANI:PSS can be removed from the PANI/UiO-66-NH₂ solid by successive washing the sample with fresh acidic solutions through centrifugation. As this is the first time reporting the PANI solely confined in the pores of a MOF, as a demonstration, the obtained PANI/UiO-66-NH₂ composite material is applied as the electrode material for supercapacitors. The PANI/UiO-66-NH₂ thin films exhibit a pseudocapacitive electrochemical characteristic, and their resulting electrochemical activity and charge-storage capacities are remarkably higher than those of the bulk PANI thin films.     

Contraction of the cyclohexene ring in the Diels–Alder adduct of levoglucosenone with piperylene

Diels–Alder adducts of levoglucosenone with piperylene were subjected to allylic oxidation–epoxidation, followed by successive functionalization of the α- and β-positions, and transformations of the resulting 1,2-epoxy derivatives under the action of boron trifluoride–diethyl ether complex and bases were studied. The most efficient was the Wagner–Meerwein rearrangement of the α-hydroxy derivative with formation of a fused cyclopentane in 39% yield.     

Formation of TiO2 ceramic foams from the integration of the sol–gel method with surfactants assembly and emulsion

A general and potentially easy method for synthesizing TiO₂ ceramic foams presenting hierarchical architecture of meso and macropores is presented here. The ceramics foaming method is based on the integration of the sol?Cgel process with sodium dodecyl sulfate (SDS) surfactant and oil droplets of isopropyl myristate (IPM) as dual pore templates. The main aim of this study was to evaluate the effect of ionic surfactant on the porous structure and specific surface area. The structural feature of these materials was characterized by analyzes of X-ray diffraction, nitrogen absorption/desorption isotherms, Hg porosimetry, He and Dried-Fluid^? picnometers. Mercury intrusion porosimetry shows that SDS and IPM induce the formation of hierarchical structure composed of two families of pores, namely macro and mesopores. The relative population of each family and the average size of macropores could be finely tuned by adjusting the SDS quantity. In the presence of this surfactant, a single anatase crystalline phase was observed for titania foams fired at 600?°C.     

Effect of the Loading of Metal Salts on the Formation of Fe–Co Solid Solution Nanoparticles in the IR-Pyrolyzed Chitosan Matrix

Russian Journal of General Chemistry - In this study, metal-carbon nanocomposites have been synthesized via the method of simultaneous formation of bimetallic Fe–Co nanoparticles and carbon...