Carbosilane dendrimers with diundecylsilyl, diundecylsiloxane, and tetrasiloxane terminal groups: Synthesis and properties

Three derivatives of poly(allylcarbosilane) dendrimers of the fifth generation with different terminal groups are synthesized. The influence of terminal groups on the properties of the dendrimers in bulk and solution is investigated by viscometry, precision adiabatic vacuum and differential scanning calorimetry, dynamic light scattering, and atomic force microscopy. It is shown that the surface layers of the dendrimers substantially affect their properties and behavior. The existence of the second relaxation transition and its dependence on the nature and structure of terminal groups are established. The experimental data indirectly confirm the assumed formation of intermolecular entanglement networks for higher generation dendrimers.     

Development and synthesis of bulk and membrane catalysts based on framework phosphates and molybdates

The scientific principles were formulated that underlie an integrated approach to development and synthesis of bulk and membrane catalysts for methanol transformation to dimethyl ether and hydrogen which are environmentally friendly fuels. The results were summarized for studies into relationships in formation of phosphates MZr₂(PO₄)₃ (M = Na, K, Rb, Cs, Mg_0.5, Ca_0.5, Sr_0.5, Ba_0.5, Zr_0.25), Cu_0.5(1+y)Fe _y Zr_2−y (Po₄)₃, molybdate phosphates Na_1−y Zr₂(Moo₄) _y (Po₄)_3−y , and molybdate Ni_0.3Cr_0.4Fe_1.4(Moo₄)₃ with the desired structure and properties controllable by variation of their chemical composition and synthesis parameters. The surface characteristics and catalytic properties of the resulting systems and the yields of the target product formed from methanol transformations in inert and oxidizing atmospheres were analyzed in relation to the catalyst synthesis condition.     

A new example of the three-component reaction: nucleophilic ring opening in cyclopropenones by cyanide ions in the presence of water or alcohols

3-Methyl-2,3-diphenyl-and 3-methyl-2-phenylcyclopropenones react with NaCN and water or alcohols as nucleophiles in the presence of NaHSO₄ to give novel compounds, namely, 3-cyano-2,3-diphenylpropionic acid or alkyl 3-cyano-2,3-diphenyl-and alkyl 3-cyano-2-methyl-3-phenylpropionates. A reaction mechanism was proposed. The anti-(R*R*)-diastereomer was found to be the major reaction product. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2066–2069, September, 2005.     

Origin of Degradation of the CaF2/BaF2 Buffer Layers on Si(111)

Doklady Physics - The growth temperature dependences of the capacitance–voltage characteristics and chemical stability of the CaF2/BaF2 buffer layers formed on Si by molecular beam epitaxy...     

Structural,chemical, and dynamic characteristics of ceramic membranes modified with self-organized supramolecular silicon oxide systems

The changes in structural characteristics, chemical composition, and gas permeability of the modified ceramic asymmetric tubular membranes were studied. The membranes were tested in permeability and selectivity of two gaseous mixtures (H/He and H/Ar). The structure of the modified coating was examined by X-ray powder diffraction and by transmission and scanning electron microscopies.     

Influence of UV Radiation on the Processes Proceeding on the Anthracene Single Crystal Surface

Russian Physics Journal - In this study, the influence of the annealing conditions on the formation of macrosteps on the anthracene single crystal surface is demonstrated. Under normal conditions...