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21.
Eishun Tsuchida Kunio Mishima Kiwamu Kitamura Isao Shinohara Setsuo Mimashi 《Journal of polymer science. Part A, Polymer chemistry》1972,10(12):3627-3637
In order to clarify the kinetic features of the styrene (A)–methyl methacrylate (B)–CCl4(S) cooligomerization system, a computer simulation was carried out. The experimental data on the degree of polymerization and the deviation of the cooligomer composition from the statistical steady-state composition were comparatively well explained by calculations based on the kinetic equations derived from the assumed reaction scheme and the values of the velocity coefficients, although the values of the four velocity coefficients in the initiation step and the velocity coefficient of the termination by the coupling of two solvent radicals were estimated. The results of the calculation of the rate of each component reaction show that the following two reactions are the most important in the initiation and in the transfer and termination steps when the [S]/([A] + [B]) ratio is large: where, A, A*, and P are styrene, polystyryl radical, and the cooligomer, respectively. Moreover, it was concluded that the deviation of the cooligomer composition from the statistical steady-state composition was caused by these two reactions. 相似文献
22.
Nomura S Itoh T Nakasho H Uno T Kubo M Sada K Inoue K Miyata M 《Journal of the American Chemical Society》2004,126(7):2035-2041
Highly conjugated monomers, 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes (methoxy (1a), ethoxy (1b), isopropoxy (1c), benzyloxy (1d), chloroethoxy (1e), and bromoethoxy (1f)), were synthesized. Recrystallizations of 1a, 1c, 1e, and 1f yielded two crystal forms (prisms (1a-A) and needles (1a-B), needles (1c-A) and plates (1c-B), prisms (1e-A) and plates (1e-B), and prisms (1f-A) and needles (1f-B)), which have different molecular packing modes by X-ray crystal structure analysis, indicating that the crystals are polymorphic. In the photopolymerizations of these monomer crystals in the solid state, 1a-A, 1e-A, and 1f-A polymerized topochemically to give crystalline polymers. For their thermal polymerizations in the solid state, in addition to 1a-A, 1e-A, and 1f-A, 1e-B and 1f-B polymerized, but polymers formed from the 1e-B and 1f-B were amorphous. The packing of quinodimethane molecules in the crystals was defined by four kinds of parameters, stacking distance (d(s)), the distance between the reacting exomethylene carbon atoms (d(cc)), the angles formed between the stacking axis and longer axis of the monomer molecule (theta(1)), and the shorter axis of the monomer molecule (theta(2)), and then the polymerization reactivity of these quinodimethanes in the solid state was discussed on the basis of these parameters. 相似文献
23.
Ramesh Chitrakar Hirofumi KanohYoshitaka Miyai Kenta Ooi 《Journal of solid state chemistry》2002,163(1):1-4
Microwave irradiation of a suspension of γ-MnOOH in a 4 mol dm−3 LiOH solution brought about a rapid formation of semicrystalline orthorhombic LiMnO2 (o-LiMnO2) within 30 min at 120°C. Cubic Li1.6Mn1.6O4 was obtained by heating o-LiMnO2 at 400°C; lithium could be topotactically extracted from Li1.6Mn1.6O4 with acid to form cubic H1.6Mn1.6O4. 相似文献
24.
Resorcinol and 5-methylresorcinol, respectively, react with 3-oxo-2-aryl-4,4,4-trifluorobutyronitrile using zinc chloride as a catalyst in dibutyl ether under the Hoesch reaction conditions to give a low yield of 3-aryl-7-hydoxy-4-trifluoromethyl- or 3-aryl-5-hydroxy-7-methyl-4-trifluoromethyl-2H-l-benzopyran-2-ones. However, the related reaction with m-methoxyphenol was found to produce poor yields of 3-aryl-7-methoxy-4-trifluoromethyl-2H-1-benzopyran-2-one and its 3,4-dihydro-4-hydroxy derivative. 相似文献
25.
26.
The interaction of water with hydrophobic surfaces is quite important in a variety of chemical and biochemical phenomena. The coexistence of water and oil can be realized by introduction of surfactants. In the case of water vapor adsorption on graphitic nanopores, plenty of water can be adsorbed in graphitic nanopores without surfactants, although the graphitic surface is not hydrophilic. Why are water molecules adsorbed in hydrophobic nanopores remarkably? This work can give an explicit insight to water adsorption in hydrophobic graphite nanopores using experimental and theoretical approaches. Water molecules are associated with each other to form the cluster of 1 nm in size, leading to a significant stabilization of the cluster in the graphitic nanopores. This mechanism can be widely applied to interfacial phenomena relating to coexistence of water and nanostructural materials of hydrophobicity. 相似文献
27.
Hirofumi Ono Hiroyuki Yamada Shigenobu Matsuda Kunihiko Okajima Takeshi Kawamoto Hideki Iijima 《Cellulose (London, England)》1998,5(4):231-247
An intensive study for aqueous microcrystalline cellulose (MCC) suspensions was carried out in view of the relationship between a viscosity and a 1H spin-spin relaxation time (T2) of water. An investigation was carried out for four suspension systems with the different particle size distributions. The proton mole ratio () of bound water against MCC particles and T2 of bound water (T2,b) were evaluated from the T2 values obtained by Carr-Purcell- Meiboom-Gill (C.P.M.G) method and those by solid echo method, respectively. As a result of these analyses, the T2,b value for the aqueous MCC suspension was evaluated as 5 × 10–3 s and it was found that the system having a larger tended to show a higher viscosity. By relating the above results to the observation of the suspensions by an optical microscope, it was concluded that a network formed by MCC particles plays an important role in generating a high viscosity of MCC suspension, and that an averaged mobility of water molecules is sensitively affected by the network structure. 相似文献
28.
Novel 1,4-elimination reaction of C,N-bis(trimethylsilyl)-C- trimethylsiloxymethylketenimine and retro Diels-Alder reaction of 2-oligosiloxanyl-5-norbornene-2-carbonitrile cleanly gave α-oligosiloxanylacrylonitriles in excellent yield. 相似文献
29.
Hamamoto H Anilkumar G Tohma H Kita Y 《Chemical communications (Cambridge, England)》2002,(5):450-451
A novel and efficient oxidative biaryl coupling reaction of phenol ether derivatives using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA), and heteropoly acid has been developed. 相似文献
30.
A new synthetic method for functionally substituted β-trimethylsilyl-α,β-unsaturated carbonyl compounds from 1-methoxy-3-phenylthio-3-trimethylsilyl-1-propene is described. 相似文献