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21.
Radiation-induced copolymerizations of perfluorovinyl acetic acid and its methyl ester with α-olefin
Mitsuo Kawaguchi Terutaka Watanabe Osamu Matsuda Yoneho Tabata Sueo Machi 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1525-1531
Homopolymerizations and copolymerizations of perfluorovinyl acetic acid (FVA) and its methyl ester (MFVA) were carried out by γ radiation at a temperature of 25°C, a dose rate of 1 × 106 rad/hr, and FVA/α-olefin and MFVA/α-olefin ratios of 10/90-90/10 in the monomer mixture. FVA and MFVA gave small quantities of brown and greasy low-molecular-weight homopolymers. The polymerization rates of both FVA and MFVA were extremely small, as shown by the maximum G value of monomer consumption of 12. FVA and MFVA reacted with α-olefin to form waxlike copolymers. The copolymerization rates of both FVA and MFVA with α-olefin were remarkably larger than those of the homopolymerizations, particularly with ethylene. The polymer compositions of FVA/ethylene or MFVA/ethylene was nearly 1/2 over a wide range of the monomer compositions. The Mayo–Lewis method gave negative r1 (FVA) and r1 (MFVA). The polymer composition curves could be well interpreted by introducing the penultimate model. 相似文献
22.
Resonance Raman scattering with the Q band of CuTPP shows a peculiar intensity pattern; bands due to combinations and overtones are strong, whereas the corresponding fundamentals are very weak. By a quantitative analysis of excitation profiles, this phenomenon has been fully accounted for on the basis of the vibronic theory of Raman intensities. Vibronic coupling parameters between the Q and B states of CuTPP have been obtained. 相似文献
23.
Mitsuo Ishikawa Hiromu Sakamoto Michie Ishii Joji Ohshita 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3281-3289
Poly[o-(tetramethyldisilanylene)phenylene] ( 2a ), poly[o-(1,2-dimethyldiphenyldisilanylene)-phenylene] ( 2b ), poly[m-(tetramethyldisilanylene)phenylene] ( 2c ), and poly[m-(1,2-dimethyldiphenyldisilanylene)phenylene] ( 2d ) were prepared by the sodium condensation reaction of the corresponding 1,2-and 1,3-bis (chlorosilyl)benzenes in toluene. Irradiation of thin films of 2a-2d in air resulted in a rapid decrease of absorption maxima in the ultraviolet region. The photolysis of 2b and 2d in benzene afforded photodegradation products with low molecular weights. When thin films of 2b and 2d were doped with antimony pentafluoride vapor, films which have conductivities of semi-conductor level were obtained. © 1993 John Wiley & Sons, Inc. 相似文献
24.
Takashi Kamimura Tsukio Masegi Mitsuo Sekine Tsujiaki Hata 《Tetrahedron letters》1984,25(38):4241-4244
Diisopropylethylamine was effective as a base for acylation of 2′,3′,5′-tri-O-acetyluridine with various acid chlorides. The 13C NMR spectra of the products and related compounds showed clearly that the acyl groups intoduced to the uracil moiety are attached to the N3-nitrogen. 相似文献
25.
The reaction of lithium ester enolate with enones provides a challenge for chemoselectivity, that is, discrimination between a conjugate addition and a 1,2-addition. Asymmetric conjugate addition of a lithium enolate of alpha-trimethylsilanylacetate to acyclic and cyclic alpha,beta-unsaturated ketones was mediated by an external chiral ligand to give the corresponding 1,4-adducts in good enantioselectivity of 74% and good chemoselectivity. 相似文献
26.
Oderaotoshi Y Cheng W Fujitomi S Kasano Y Minakata S Komatsu M 《Organic letters》2003,5(26):5043-5046
High diastereo- and enantioselectivities were obtained for the asymmetric 1,3-dipolar cycloaddition of azomethine ylides generated from N-alkylideneglycine esters with dipolarophiles using chiral phosphine-copper complexes as catalysts. Whereas the cycloaddition of azomethine ylides catalyzed by metal salts generally afforded endo-adducts as the predominant product, the present method is the first example of an exo-selective cycloaddition. [reaction: see text] 相似文献
27.
A methanol extract from Prunus mume Sieb. Et Zucc. showed a suppressive effect of the SOS-inducing activity on the mutagen 3-amino-1,4-dimethyl-SH-pyrido[4,3-b]indole(Trp-P-1) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, ethyl acetate, butanol and water. The dichloromethane and ethyl acetate fractions showed suppressive effect. Suppressive compounds were isolated by silica gel column chromatography and identified as trimethyl citrate (1) and dimethyl citrate (2) by GC-MS, IR and 1H and 13C-NMR spectroscopy. Compounds 1 and 2 suppressed 51 and 39% of the SOS-inducing activity at a concentration of 2.0 micromol/mL. 相似文献
28.
Takashi Tateno Shinji Doi Shunsuke Sato Luigi M. Ricciardi 《Journal of statistical physics》1995,78(3-4):917-935
Noise effects on phase lockings in a system consisting of a piecewise-linear van der Pol relaxation oscillator driven by a periodic input are studied. The problem of finding the period of the oscillator is reduced to the first-passage-time problem of the Ornstein-Uhlenbeck process with time-varying boundary. The probability density functions of the first-passage time are used to define the operator which governs a transition of an input phase density after one cycle of the oscillator. Phase lockings in a stochastic sense are investigated on the basis of the density evolution by the operator. 相似文献
29.
30.
Tominaga Keii Yoshiharu Doi Hiromu Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》1973,11(8):1881-1888
Mass transfer which affects the rate of propylene polymerization with titanium trichloride–triethylaluminum, has been evaluated by use of a new method developed for this heterogeneous reaction. The polymerization was carried out with the usual flask reactor equipped with a paddle stirrer; the rate of gas absorption into the polymerization slurry was proportional to stirring speed and the reciprocal of the total amount of polymers produced. It has been confirmed that the polymerization rate separated from the absorption rate is purely kinetic (propagation), and an effective physical process, such as monomer transfer through a polymer film covering the catalyst surface, no longer exists. 相似文献