Adaption of the Mechanism of Emulsion Polymerization to New Experimental Results

Summary: New experimental investigations of the 'classical' batch ab-initio emulsion polymerization of styrene reveal the important role of monomer droplets for the whole process. Monomer droplets with a size between a few and some hundreds of nanometers, which are formed by spontaneous emulsification as soon as styrene and water are brought into contact, have a strong influence on the particle nucleation, the particle morphology, and the swelling of the particles. Experimental results confirm that micelles of low molecular weight surfactants are not a major locus of particle nucleation. Brownian dynamics simulations show that the capture of matter by the particles (monomer or radicals) strongly depends on the polymer volume fraction and the size of the captured species (primary free radicals, oligomers, single monomer molecules, or clusters).     

Reactions of nitronates derived from simple nitro alkanes with some thio-stabilized cationic intermediates

Trimethylsilyl and DBU nitronates derived from nitromethane and nitropropanes do not undergoC-alkylation by episulfonium (ESI) or thiophanium (TPI) cationic intermediates. The above-mentioned derivatives of 1-nitropropane react with ESI and TPI to give the corresponding products ofO-alkylation of 1-chloro-1-oxyiminopropane. The reactions of DBU nitronates derived from nitromethane and 2-nitropropane with ESI or TPI proceed asO-alkylation followed by standard fragmentation of the initially formed nitronate intermediates to give methyl (4-tolylthio)acetate or methyl 2,2-dimethyl-3-methyloxy-(4-tolylthio)butanoate respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 492–498, March, 1999.     

N-(2-Thenyl)derivatives of aminoalkyltriethoxysilanes,-silatranes and 2,2-dimethyl-1,3-dioxa-6-aza-silacyclooctane

The reactions of aminoalkylethoxysilanes and 2,2-dimethyl-1,3-dioxa-6-aza-2-silacyclooctane with 2-(chlormethyl)thiophene and its 5-chloroderivative lead to the correspondingN-(2-thenyl) derivatives. TheN-methyl-N-(2-thenyl)aminomethyltriethoxysilane and 5-chlorothyenyl derivative formed are converted by triethanolamine into silatranes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 384–386, February, 1995.     

Modulation of diarylethene fluorescence by photochromic switching and solvent polarity

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Transport properties of polyimides derived from benzophenonetetracarboxylic dianhydride and other diamines

Gas-separating membrane characteristics of polyimide films composed of the common fragment of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride and diamines of varying structure were studied. Permeability coefficient P, diffusion coefficient D, and solubility coefficient S for H₂, CO, CO₂, and CH₄ were determined. The polyimide derived from m-phenylenediamine exhibited the best gas-separating properties. A relationship between the chain rigidity, free volume, and transport parameters (P, D, S, and selectivity) of polyimide was established on the basis of the data. It was shown that there is an optimal chain rigidity for the studied polyimides that results in polymer structurization during film preparation and corresponds to high separation selectivity.     

<Emphasis Type="Italic">N</Emphasis>-(silylmethyl)amines, -amides,and -amino acids: biological activity and prospects in drug synthesis

The data on biological activity of the compounds with the geminal fragment N-C-Si are systematized. The examples of using N-(silylmethyl)amines and related compounds in syntheses of biologically active substances, including natural compounds, are considered.     

The study of the nuclear reactions for the production of antimony isotopes

Nuclear reactions using proton beams and tin targets are studied in order to obtain antimony radionuclides. A new target system that includes on-line monitoring of target heating is used. To determine the parameters of proton beams, experimental studies on nuclear reactions are performed using Ti, Cu and stainless steel targets. Using modern model approximations, cross sections are determined for the formation of radionuclides ¹¹⁹Sb and ¹¹⁷Sb in the investigated nuclear reactions.     

Rheological and Magneto-Rheological Properties of Formulations Based on Magnetite and Aqueous Emulsions of Water-Soluble Polymers in Transformer Oil

Rheological and magneto-rheological properties of magnetite dispersions in transformer oil were studied as influenced by the concentration of a modifying solution of water-soluble polymers (polyvinyl alcohol and carboxymethyl cellulose) and by the magnetic field strength.