New method for controlled synthesis of polylactide block copolymers: organoborane/p-quinone system and reversible-deactivation radical polymerization

We developed a new approach to obtain polylactide hybrid block copolymers with vinyl monomers (styrene, methyl methacrylate, methyl acrylate) through the realization of a reaction sequence using triethylborane and various p-quinones. The method offered includes two stages. In the first stage, a chain-transfer agent was obtained by borylation of the terminal hydroxyl groups of polylactide. The second stage was vinyl monomer radical polymerization in the presence of p-quinone accompanied by S_H2-substitution at the boron atom.1,4-Naphthoquinone, 2,3-dimethyl-1,4-benzoquinone, duroquinone and 2,5-di-tert-butyl-1,4-benzoquinone were used as synthetic polymer chain growth mediators. It is shown that 1,4-naphthoquinone and 2,3-dimethyl-1,4-benzoquinone, similar in their characteristics, are effective agents providing the realization of reversible-deactivation radical polymerization. Realization of reversible-deactivation radical polymerization was proved with the analysis of the kinetics of block copolymerization, molecular weight characteristics and compositional homogeneity of block copolymers as well as its further capability to elongate the polymer chain. Synthesized block copolymers have a high thermal stability compared to the initial borylated polylactide. © 2021 Society of Industrial Chemistry.     

Preparation of Hard Alloy WC and WC – Co Mixtures with Reduction and Carbidizing Treatment of Oxidized Tungsten Containing Scrap

A method of single-stage reduction and carbidizing treatment of oxidized tungsten containing scrap (hard alloys of the VK type and tungsten wire) is proposed. Procedures are suggested for preparing very fine tungsten carbide of stoichiometric composition without adding carbon black by reduction and carbidizing treatment of oxidized tungsten wire scrap and also with introduction of solid carbon (carbon black) during reduction and carbidizing treatment of oxidized hard alloy scrap.     

Measuring individual and cultural differences in implicit trait theories.

A new measure of implicit theories or beliefs regarding the traitedness versus contextuality of behavior was developed and tested across cultures. In Studies 1 (N = 266) and 2 (N = 266), these implicit beliefs dimensions were reliably measured and replicated across U.S. college student samples and validity evidence was provided. In Study 3, their structure replicated well across an individualistic culture (the United States; N = 249) and a collectivistic culture (Mexico, N = 268). Implicit trait and contextual beliefs overlapped only modestly with implicit entity theory beliefs and were predicted by self-construals in ways that generally supported cultural psychology hypotheses. Implicit trait beliefs were fairly strongly endorsed in both cultures, suggesting that such beliefs may be university held. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Designing Phase Selectively Soluble Polymer-Supports for Dimethylaminopyridine and Phosphine-Ligated Pd(0) Catalysts

Soluble poly(4-alkylstyrene) containing 4-methyl-, 4-tert-butyl, 4-dodecyl-, and 4-octadecylstyrene were formed either with monomers containing dyes-, ligands, or catalysts or with 5–10 mol% of 4-chloromethylstyrene and studied as supports for ligands or catalysts. Studies with dye-labeled polymers showed that polymers containing longer alkyl groups alone or at ca. 10 mol% loading are highly soluble in heptane can be used to separate and recycle organo- and transition metal catalysts.

     

Fabrication of Surface-Modified One-Dimensional Titania Nanostructures in the Presence of Chitosan

One-dimensional TiO₂-based nanostructures with modified surface have been produced by alkaline hydrothermal treatment of TiO₂ and CoTiO₃ powders in the presence of bioactive natural polymer—chitosan—as the organic reagent. Nanostructures are characterized by multilayer morphology. However, characteristic interlayer distances are significantly higher than in those produced without chitosan. Moreover, thin bioorganic layers are observed on the surface of elongated structures produced by processing of TiO₂ powder. Quite different surfaces with numerous Co-containing agglomerates of chitosan derivatives are detected when CoTiO₃ powder is processed. After vacuum treatment at 600°C and higher, Co-containing elongated nanostructures demonstrate the abnormal high ferromagnetic properties.     

Getting and X-ray Diffraction Analysis of the Microsphere Catalyst U,Nd on the Basis Fly Ash of Thermal Power Plants

To study the physical and chemical properties of aluminosilicate microsphere catalyst by impregnation and calcination us was first obtained aluminosilicate microsphere catalyst U, Nd for petrochemical processes. The method of X-ray structure has been studied for the microsphere catalyst U, Nd.     

Study of the chemical composition of suspended particles in Lake Baikal

Samples of suspended material (solid particles) from Lake Baikal were analysed by using X‐ray fluorescence elemental analysis with the excitation of monochromatized synchrotron radiation (SRXFA, Novosibirsk, Russia) and electron probe X‐ray microanalysis (EPXMA, Antwerp, Belgium). The chemical composition of particles in different depths and basins of the lake is discussed. The chemical composition of the central parts of the lake are stable, but concentrations are higher in the southern basin, which is liable to pollution.     

Dilution methods to deprive Chlamydomonas reinhardtii cultures of sulfur for subsequent hydrogen photoproduction

Sulfur deprivation of Chlamydomonas reinhardtii cultures gradually inactivates photosynthetic O₂ evolution and leads to the establishment of anaerobiosis in the medium. Sulfur-deprived algal cultures kept under anaerobic conditions will then produce H₂ gas for 3–5 days under continuous illumination. Currently, sulfur deprivation is achieved by mechanical centrifugation of cultures grown in sulfur-replete medium, followed by extensive and costly washing. The cells are finally resuspended in sulfur-free medium. The current study investigates two procedures to deprive algal cultures of sulfur that eliminate the centrifugation step. These procedures involve sulfur deprivation by dilution of sulfur-replete cultures into either sulfur-limited medium or sulfur-free medium. We demonstrate that efficient H₂ photoproduction can be achieved on a timely basis using either procedure. However, the dilution of sulfate-replete algal cultures 1:10 v/v into sulfur-free medium is the most appropriate procedure. These observations serve as the basis for developing an algal H₂-production system that is cheaper, less time-consuming, and less amenable to contamination with other microorganisms than systems employing centrifugation for sulfur deprivation.     

Cathode structure optimization for air-breathing DMFC by application of pore-forming agents

The cathode catalyst layer in an air-breathing, direct methanol fuel cell (DMFC) has been improved by addition of pore-forming materials, such as ammonium carbonate and ammonium hydrocarbonate. These construct an effective electrode pore structure. During fabrication of the membrane electrode assembly (MEA), these pore-formers decompose, increase the BET surface area of the electrodes, and form additional porosity. Ammonium carbonate predominantly produces macropores, while ammonium hydrocarbonate is effective for mesopores. This results in an increase in electrochemical active area and catalyst utilization. The higher open-circuit voltage with MEAs prepared with pore-forming material indicates improved air transfer through the cathode. The power density is increased by 30–40% with the employment of the pore-forming materials.