Synthesis and properties of siloxane(ethylene oxide)urethane block copolymers

A new approach to the synthesis of hydrolytically stable dimethylsiloxane-ethylene oxide polyblock copolymers is described, in which ethylene oxide and siloxane blocks are linked by urethane groups. The molecular-mass parameters of block copolymers of different compositions are determined by capillary viscometry, light scattering, and gel-permeation chromatography. The temperature transitions in copolymers are characterized by differential scanning calorimetry.     

H, V and N nuclear magnetic resonance studies of structure and properties of vanadia supported on TiOx/SiO2

¹H magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of TiO_x/SiO₂ catalysts suggest the interaction of surface TiO_x. species with Si-OH groups of the silica. Simultaneously, Ti-OH groups from surface titania species appear. The distribution of TiO_x species over SiO₂ is non-uniform, since a considerable part of surface OH groups remains unreacted with supported titania. Supported vanadia species interact both with Si-OH and Ti-OH groups. ⁵¹V NMR spectra suggest the interaction of vanadia with supported titania species and show the non-uniform distribution of titania over the SiO₂ surface. Deposition of titania as well as vanadia produces strong electron-accepting (Lewis) sites which interact with the terminal N atom of adsorbed N₂O molecules, resulting in a downfield shift of the resonance in ¹⁵N NMR spectra. The acid strength of electron-accepting sites is similar in both cases. Only about 10% of the total amount of supported titania and vanadia create Lewis sites.     

Dependence of the structure of siloxane urethane elastomer on the conditions of synthesis

The morphology and thermal and mechanical properties of siloxane urethane block copolymers based on oligosiloxane- and oligoalkylene diols are investigated. The dependence of morphology on the conditions of synthesis is studied via atomic force microscopy and scanning electron microscopy.     

Unusual oxidative cleavage of the aryl—ethynyl bondsin (arylethynyl)polymethylbenzenes with iodine in dimethyl sulfoxide

While heating 1,2,4,5-tetramethyl-3,6-bis(phenylethynyl)benzene, 1,3,5-trimethyl-2,4-bis(phenylethynyl)benzene, and 1,2,4,5-tetramethyl-3-(phenylethynyl)benzene with iodine in DMSO in the absence of oxygen, the triple bonds are oxidized to give the corresponding 1,2-diketones. In the presence of oxygen, the previously unknown competitive oxidative process causes the cleavage of the aryl—ethynyl bonds so that duroquinone and the corresponding 4-hydroxybenzils are formed. This cleavage is produced by oxygen only in the presence of iodine and DMSO. It was shown that the key stage of the process is the formation of intermediate charge-transfer complexes between polymethylbenzene rings and iodine.     

Modification of petroleum polymer resin from C9 fraction with maleic acid and its application to protecting treatment of wood

Modification of petroleum polymer resin with maleic acid is studied and changes in acid number, molecular weight and bromine number of the forming product in time are determined. The modified petroleum polymer resin is shown useful for enhancing hydrophobic properties of wood.     

Surface Properties of γ-Alumina Deposits on Highly Permeable Cellular Carriers

The electron–acceptor properties and the hydroxyl cover of the surface of a secondary support, -Al₂O₃ deposited on highly porous permeable cellular materials of corundum and Nichrome, were studied. The effect of lanthana additives on the acid–base properties of the surface of this support was also studied. The surface properties of the secondary support are typical of -Al₂O₃. The type of highly permeable porous cellular materials used and the modifying additives influence both the acidity of hydroxyl groups and the strength and concentration of electron-acceptor sites.