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761.
Sergei S. Sheiko Gabi Eckert Galina Ignat'eva Aziz M. Muzafarov Jochen Spickermann Hans J. Rder Martin Mller 《Macromolecular rapid communications》1996,17(5):283-297
Adsorption and aggregation of carbosiloxane dendrimers on mica and pyrolytic graphite were investigated by scanning force microscopy (SFM). The aggregation process started from (i) single molecules which coagulated to (ii) clusters and (iii) fluid droplets followed by formation of (iv) a complete layer on the solid substrate. The molecules were displayed as a globular particle with a diameter of about 2.5 nm. Tapping SFM of the liquid was possible due to the fact that the dendrimer undergoes a transition to a viscoelastic state below the tapping frequency of about 360 kHz. Dynamic shear compliance experiments have shown a plateau of 5 · 10−7 Pa−1 around this frequency. Dendrimer droplets slowly spread into polygonal lamellae with a thickness of two molecular layers. The structures indicate a rather regular dense packing of the globular molecules. 相似文献
762.
Journal of Solid State Electrochemistry - 相似文献
763.
A system involving homopolymerisation of a 3‐functional monomer has been studied by using an off‐lattice long‐range percolation model. The elementary reaction steps were controlled by substitution effects and by local concentrations of units. The latter were controlled by setting a constant value to a range‐of‐reaction parameter called the capture radius. The critical conversion at gelation in the system turned to the classical one as the value of capture radius increased. 相似文献
764.
Vladimir I. Lozinsky Roman V. Ivanov Elena V. Kalinina Galina I. Timofeeva Alexei R. Khokhlov 《Macromolecular rapid communications》2001,22(17):1441-1446
The radical polymerisation of acrylamide initiated with a persulfate/tertiary amine redox pair was performed in liquid (+5 to +35°C) and moderately frozen (–10 to –30°C) aqueous solutions. The reaction in frozen systems resulted in the pronounced increase in the molecular weight of the polymer. The temperature dependence of the yield and molecular weight of cryogenically produced polyacrylamide were of extreme character with a maximum for both parameters in the vicinity of –12.5°C. 相似文献
765.
Badma N. Mankaev Valeriia A. Serova Dr. Mikhail A. Syroeshkin Anna Ya. Akyeva Dr. Alexey V. Sobolev Dr. Andrei V. Churakov Dr. Elmira Kh. Lermontova Dr. Mikhail E. Minyaev Dr. Yury F. Oprunenko Dr. Maxim V. Zabalov Kirill V. Zaitsev Dr. Galina S. Zaitseva Prof. Dr. Sergey S. Karlov 《欧洲无机化学杂志》2023,26(11):e202200690
A series of novel tetrylenes based on three 2,6-bis(2-hydroxyphenyl)pyridines 4 a – 4 c have been obtained by the reaction of Lappert's tetrylenes E[N(SiMe3)2]2 (E=Ge, Sn) with corresponding tridentate pyridine-linked phenol-based ligands. It was found that the structure of the ligand and the size of the atom of the group 14 element drastically affect the structure of the reaction product. Ligand 4 c with a bulky tert-butyl group leads to monomeric tetrylenes, while ligands with less bulky groups lead to bis-ligand derivatives of M(IV) (M=Ge, Sn) and a coordination polymer. Also, derivatives of germanium (IV) and tin (IV) were obtained by the metathesis reaction of MCl4 (M=Ge, Sn) with lithium phenoxides. The compositions and structures of the novel compounds were established by elemental analysis and 1H, 13C, 119Sn ( 5 – 7 ), 1H DOSY ( 6 ) NMR spectroscopy, in the solid state by X-ray diffraction analysis (germylene 10 , stannylene 6 , Ge4+ compound 8 , Sn4+ compound 7 ) and 119Sn Mössbauer spectrum of tin complex 6 . All the synthesized tetrylenes are monomeric. Tetrylenes 6 and 10 were characterized by cyclic voltammetry. A study of the redox behavior of 6 , 10 by cyclic voltammetry on a glassy carbon working electrode in acetonitrile solution of 0.1 M Bu4NPF6 as a supporting electrolyte showed that these compounds can be both oxidized and reduced electrochemically in the accessible potential range. 相似文献
766.
Computer simulations of the step-growth homopolymerization of an AB2 monomer have been carried out on a square lattice. No rearrangements of units were made between reaction events. Instead, the capture radius, i.e., the maximum distance between the randomly selected unit and its reaction partner was changed. The reaction was considered as controlled either by diffusion and local concentration fluctuations or by the law of mass action (classical limit). The size distribution of polymer species and the extent of cyclization reactions in the polymerization are discussed. 相似文献
767.
Tatiana Sukhanova Vladimir Bershtein Mimi Keating Galina Matveeva Milana Vylegzhanina Victor Egorov Nina Peschanskaya Pavel Yakushev Edmund Flexman Stefan Greulich Bryan Sauer Kathleen Schodt 《Macromolecular Symposia》2004,214(1):135-146
Comparative WAXD/SAXS/SEM/DSC structural studies of a series of semi-crystalline poly(oxymethylene) (POM) engineering plastics, including the commercial products, homopolymer Delrin® and typical poly(oxymethylene-co-oxyethylene)s, and a few lab-made POM compositions, were performed. The latter differed in their content of functional additives (present in low concentrations) and POM molecular weight characteristics. In parallel, their densities, thermal behavior/laser-interferometric creep rate spectra (DSC/CRS) at 20-180 °C, as well as long-term creep resistance (LTCR) at 20 °C were studied. It has been found that introducing the nucleating agents and oxyethylene units resulted in formation of more fine spherulitic or practically non-spherulitic structure with close- or loose-packed lamellar stacks. The presence of both “thick” (5-10 nm) and “thin” (1.5-3 nm) lamellae in the weight ratio of ∼3:1 was shown in all cases. Close values of real POM crystallinities, not exceeding 50%, were obtained by WAXD and DSC. A predominant role of “straightened out” or slightly bent tie chains in disordered layers of isotropic POMs was presumed, resulting in segmental dynamics differently constrained by crystallites (DSC/CRS data). As a result, certain morphology - density - creep resistance correlations were found. 相似文献
768.
A new kinetic scheme for chain transfer to monomer in the anionic polymerization of hydrocarbon monomers is presented. The scheme agrees with generally accepted views on the chemical mechanism of carbanionic reactions better than the one used previously. It is suggested that the most probable path of the transfer reaction is the proton abstraction from the side group of the monomer, the terminal double bond of the monomer molecule remains unchanged, and therefore the intermediate species can participate in succeeding reactions as a macromonomer. The discrepancy between the predictions of the proposed scheme and of the previous one concerning the molar characteristics of polymers are discussed and the ways to establish the true mechanism of transfer in particular systems are suggested. 相似文献
769.
Galina I. Litvinenko Alexander A. Arest-Yakubovich 《Macromolecular theory and simulations》1993,2(6):929-938
The main factors determining molar mass characteristics of copolymers formed in nonterminating copolymerization under the conditions of chain transfer to solvent are studied theoretically. The dependences of the mean polymerization degrees on conversion and monomer feed composition for various values of reactivity ratios are obtained. The results obtained greately differ from those for homopolymerization. This is explained by the contribution of cross-propagation reactions. In particular, it is shown that at ≪ and ≪ the azeotropic copolymerization proceeds like the living one even if homopolymerization of each monomer is accompained by extensive chain transfer to solvent. 相似文献
770.
Galina Abramova Juerg Schefer Nadir Aliouane Martin Boehm German Petrakovskiy Alexandr Vorotynov Mikhail Gorev Asya Bovina Vladimir Sokolov 《ChemInform》2015,46(22):no-no
Single crystals of the α-MnS-based FexMn1-xS (x = 0-0.3) solid solutions are prepared and shown to be new Mott materials with the rock salt structure. 相似文献