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排序方式: 共有253条查询结果,搜索用时 15 毫秒
211.
Naofumi Naga Hiroki Sakai Chiharu Usui Haruhiko Tomoda 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3542-3552
Copolymerizations of ethylene or propylene and allyl monomers containing 9‐fluorenyl group, diallyl‐di‐9‐fluorenylsilane (DAFS), 9,9‐diallylfluorene (DAF), and 9‐allylfluorene (AF), were investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged zirconocene catalysts, especially a syndioselective catalyst, showed a higher reactivity for all the comonomers than the nonbridged catalysts. DAFS was mainly incorporated into the polymer chain via cyclization insertion, whereas DAF was copolymerized via both 1,2‐ and cyclization insertions. Cyclization selectivity, ratio of cyclized insertion unit, of DAF in the copolymerization with propylene was higher than that in the copolymerization with ethylene. Copolymerization with AF yielded low‐molecular weight copolymer because of frequent chain transfer reaction. Optical properties of the propylene based‐copolymers were investigated by UV‐vis and photoluminescence spectroscopy, and absorption‐ and emission‐derived from fluorenyl groups were detected in the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3542–3552, 2010 相似文献
212.
Yukio Hitotsuyanagi Genta Shigemori Haruhiko Fukaya Maho Hikita Shu Zhu Katsuko Komatsu Koichi Takeya 《Tetrahedron letters》2013
Three new alkaloids, stemona-amines C–E, were isolated from the roots of Stemona tuberosa Lour. (Stemonaceae). The structures of stemona-amines C and D were determined by X-ray crystallography and that of stemona-amine E was determined by interpretation of spectroscopic data. The absolute structures of stemona-amines C and D were established by VCD spectroscopy. 相似文献
213.
Naofumi Naga Yoshikazu Ohkura Nanae Tagaya Haruhiko Tomoda 《Journal of polymer science. Part A, Polymer chemistry》2011,49(23):4935-4940
Alternating copolymerization of 9,9‐bis(3,6,9‐trioxadecyl)‐2,7‐dibromofluorene (ODFl) or 9,9‐bis(3,6‐dioxaheptyl)‐2,7‐dibromofluorene with Si containing divinyl compounds, divinyldiphenylsilane (VPS), or divinyldimethylsilane (VMS) is investigated using the Mizoroki–Heck reaction with palladium(II) acetate. The corresponding alternating copolymer is obtained in the copolymerization of ODFl with VPS. The copolymerization of ODFl with VMS yields low molecular weight oligomers. Optical properties of the ODFl–VPS copolymer have been investigated with UV–vis absorption and photoluminescence (PL) spectroscopy. The ODFl–VPS copolymer shows absorption peaks due to π–π* transition and intramolecular charge transfer through σ–π moiety at around 330 and 360–400 nm, respectively. An emission peak is observed at 450 nm in the PL spectrum of the ODFl–VPS copolymer, and the PL quantum yield is 0.19. The PL spectroscopy of ODFl–VPS copolymer is investigated in the presence of Li+, Na+, and K+, and the intensity of emission peak is decreased by those metal cations, especially by Na+. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
214.
215.
Vitalij I. Volkov Svetlana A. Korotchkova Haruhiko Ohya Qunhui Guo 《Journal of membrane science》1995,100(3):273-286
The self-diffusion of water, ethanol and water-ethanol mixtures in polyacrylic acid (PAA) and PAA-polysulfone (PSF) composite membranes was measured with pulsed-field gradient (PFG)-nuclear magnetic resonance (NMR) spectroscopy. The partial solubilities and self-diffusion coefficients were obtained. An attempt was made to explain the transport properties of water and ethanol through the PAA layer and PAA-PSF composite membranes. It was concluded that there are two types of channels for diffusate transfer in PAA: an ionogenic hydrophilic channel which is selective for water and a hydrophobic channel which contains a predominance of ethanol molecules. The existence of aluminum nitrate in PAA influences the morphology of the latter channel. There is a good agreement between of the separation factors estimated from PFG-NMR data and those obtained by pervaporation testing. 相似文献
216.
217.
Haruhiko Furukawa Tadao Kanzaki Takashi Katsura 《Journal of Electron Spectroscopy and Related Phenomena》1985,36(1):1-10
The X-ray photoelectron spectra of Mo 3d electrons (232.4–232.9 and 229.4–229.6 eV) for Mo-bearing ferrites have suggested that molybdenum ions are in the 4+ valence state on the lattice points in the spinel structure. The XPS data for Mo 3d and Fe 2p electrons combined with the Mössbauer data at room temperature suggest that Fe2MoO4 takes a valence state (Fe2+)tet[Fe2+Mo4+]octO4. 相似文献
218.
Kazuo Tori Isao Horibe Youko Tamura Kaoru Kuriyama Haruhiko Tada Kenichi Takeda 《Tetrahedron letters》1976,17(5):387-390
219.
Kohji Seio Takeshi Terada Masahiro Mizuta Akihiro Ohkubo Haruhiko Taguchi Mitsuo Sekine 《Helvetica chimica acta》2007,90(10):1946-1965
New oligonucleotides with a long‐chain linker (6,9‐dioxa‐3,12‐diazatetradecane‐1,14‐diyl) in their backbone were synthesized, and their hybridization properties were studied by measurement of their Tm curves and fluorescence spectra. The Tm analyses revealed that these oligonucleotides could bind to their complementary strands despite the presence of the long‐chain linker. We also demonstrated interesting fluorescence properties of oligodeoxynucleotides with an anthracen‐9‐ylmethyl group on one of the two N‐atoms in the long‐chain linker. The fluorescence intensity of these oligonucleotides increased upon their hybridization to the complementary strands and was sensitive to the presence of the mismatch base pairs at a specific position. 相似文献
220.
Kaneda M Nakamura A Asaoka S Ikeda H Mori T Wada T Inoue Y 《Organic & biomolecular chemistry》2003,1(24):4435-4440
Pressure effects on enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-cycloocta-1,5-diene sensitized by chiral benzene-1,2,4,5-tetracarboxylate were investigated over a pressure range of 0.1-750 MPa. Enantiomeric excesses (ee's) of the (E)- and (E.Z)-isomers obtained displayed discontinuous pressure dependencies, affording distinctly different differential activation volumes (delta delta V++) for each range, indicating alteration of the enantiodifferentiation mechanism. The switching of delta delta V++ occurred at essentially the same pressures of 200 and 400 MPa, which are shared by all the chiral sensitizers, irrespective of the chiral auxiliary employed. Circular dichroism spectral examinations at pressures of up to 400 MPa also revealed that the chiral sensitizers undergo discontinuous conformational changes at 200 MPa, which most likely lead to switching of the enantiodifferentiating sensitization mechanism in the exciplex intermediate. 相似文献