Yu. A. Kabachii

Alcoholysis and aminolysis of Di-and trithioester chain-transfer agents of free-radical polymerization

The alcoholysis and aminolysis of (S)-1-phenylethyl-(O)-ethyl dithioxanthate, 1-phenylethyl dithiobenzoate, and bis(1-phenylethyl) trithiocarbonate have been studied. These compounds model end groups of polystyrenes prepared by the controlled radical polymerization carried out in the presence of di-and trithioesters. It has been shown that the yield of 1-phenylethylthiol is markedly dependent on the structure of ester. Possible mechanisms governing side reactions are considered, and conditions providing the quantitative yield of polystyrenes with end thiol groups have been estimated.

Dithioesters in atom-transfer radical polymerization

Phenyl dithioacetates and bis(isobutyl) dithiocarbamates of Cu(II) and Ti(IV) were studied as chain-transfer agents in the controlled free-radical polymerization of methyl methacrylate and styrene. It was shown that the above compounds strongly decelerate the polymerization of at least one of the monomers. When Cu(II) bis(isobutyl) dithiocarbamate was used in an equivalent ratio with an initiator, the polymerization of MMA proceeded as a well-controlled process and yielded a monodisperse polymer. In other cases, when the concentration of the salt was reduced by two or more times, the most reliable feature of controlled polymerization was observed; that is, the molecular mass of the polymer increased linearly and progressively with an increase in the monomer conversion. The results obtained confirmed that dithiocarboxylate and dithiocarbamate groups can, similarly to halides, interact with transition-metal compounds through ligand-(atom)-transfer redox reactions.

Synthesis and Study of Self-Organization of Organo–Inorganic Nanostructures Based on Cationic Poly(meth)acrylates and Molybdenum Disulfide Single Layers

Poly(meth)acrylates of three types, namely, regular homopolymers containing side-chain tetraalkylammonium ionic groups with alkyl radicals of various lengths (C6 and C16), a copolymer with statistically distributed ionic and long-chain (C18) alkyl groups, and a block copolymer of the same composition in which alkylammonium and alkyl groups are located in separate blocks, are synthesized with the use of controlled radical polymerization processes. The interaction of the polymers with molybdenum disulfide singlelayer dispersions yields self-organized organic-inorganic nanocomposites containing up to 40% polymer. As evidenced by powder X-ray diffraction and high-resolution transmission electron microscopy structural studies of the composites, they possess a crystalline layered structure with interlayer distances depending on the composition and structure of the polymer. Structures with the most regular alternation of organic and inorganic layers are formed in the case of homopolymers. The orientation of their alkylammonium fragments relative to MoS2 layers depends on the length of the alkyl radical and corresponds to their parallel (C6) or perpendicular (C16) arrangement.

Heterogeneous catalysis in ionic liquids: The heck reaction of bromobenzene with styrene over palladium supported on mesoporous carbon

Tributylhexylammonium bistriflamide [(C4H9)(C6H13)N][(CF3SO2)2N], an ionic liquid, was used as a solvent for the Heck reaction of bromobenzene with styrene in the presence of Pd deposited onto a mesoporous carbon support. It was found that dibutylamine used as a basic reagent to scavenge hydrogen bromide results in higher conversions of the reactants and higher yields of stilbene than sodium acetate. It was shown that the IL is fully recoverable after use in the catalytic reaction.

Hydrophilization of CdS nanoparticles using a polymeric coating and their photocatalytic properties

The method for the preparation of stable aqueous dispersions of CdS nanocrystals synthesized by the thermal decomposition of cadmium oleates in the presence of sulfur due to surface functionalization by cationic comb-shaped copolymer of 2-(methacryloyloxy)ethyltrimethylammonium methyl sulfate and stearyl methacrylate is presented. The hydrophilization of the CdS nanoparticles does not noticeably change their size, phase composition, and optical characteristics. The functionalized particles exhibit photocatalytic activity in the reaction of water splitting, which strongly depends on the content of the Pt cocatalyst.

The heterogeneous catalytic heck reaction in an ionic liquid

The C-C cross coupling reaction between bromobenzene and styrene in the presence of Pd deposited on mesoporous acetylene soot (Pd/C) occurred in a tetraalkylammonium ionic liquid (IL) as a truly heterogeneous catalytic process. The active palladium form was not transferred into the reaction solution. Deposited palladium activation was observed when the Pd/C catalyst was preliminarily heated in the IL in the presence of dibutylamine as a base.

Catalytic activity of Pt-promoted CdS nanocrystals covered with a polymer in photoelectrochemical hydrogen production by water splitting

Photocatalytic properties of Pt-promoted CdS nanocrystals functionalized by the polymer coating were investigated. Deposition of Pt on the surface of the nanoparticles followed by polymer functionalization provides a high photocatalytic activity (1.45 mmol h–1 mg–1 at 0.93 W cm–2) and apparent quantum yield (7%, λ = 445 nm) of the particles. Dependence of the rate of H2 evolution on Pt loading is described by a curve with the maximum, whereas the quantum yield decreases with an increase in the light flux density. The photocatalytic activity of the nanocrystals increases more than 2 times with polymer coatining.

Addition of thiol-ended polystyrene to acrylates

Polystyrene containing end thiol groups has been prepared via the aminolysis or alcoholysis of its trithioester under conditions established previously for the model reaction of bis(1-phenylethyl) trithiocarbonate. The aminolysis of polystyrene with Mn = 8.2 × 103 by n-hexylamine at 100°C in toluene led to the formation of a polymer with Mn = 4 × 103 and a polydispersity coefficient of 1.13. The unimodal molecular-mass distribution of the polymer and its narrow polydispersity that is nearly equal to the initial polydispersity suggest that all trithiocarbonate groups of the starting polystyrene are involved in hydrolysis. The addition of 1-phenylethylthiol and thiol-ended polystyrene to methyl acrylate and methyl methacrylate via the Michael hydrolysis has been studied, and it has been demonstrated that the addition proceeds quantitatively at room temperature. The addition may be directly implemented with the use of dithioesters in the presence of the catalytic amount of a base; therefore, the stage of thiol synthesis can be eliminated. For the quantitative addition to acrylates, the preliminary hydrolysis of the polymer is however preferable.

Synthesis of amphiphilic block copolymer from optically active N-benzylprolinol acrylate

A vinyl monomer N-benzylprolinol acrylate has been synthesized from the available amino acid enantiomer L-proline via four stages. An optically active amphiphilic block copolymer capable of phase microsegregation in aqueous solutions has been synthesized through controlled free-radial polymerization of this monomer using poly(ethylene oxide) containing terminal 2-bromoisobutyrate groups as a macroinitiator.

Condensation of carboranes-12 with tri- and tetrachloroethylenes

The interaction ofortho-, meta-carboranes with tri- and tetrachloroethylene was investigated at 380°C in the absence of radical sources and at 150–200°C in the presence oftert-butyl peroxide.