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101.
Hideyuki Higashimura Kiyoshi Fujisawa Shuhei Namekawa Masaaki Kubota Akinobu Shiga Yoshihiko Moro‐Oka Hiroshi Uyama Shiro Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》2000,38(Z1):4792-4804
Various effects on the coupling selectivity of the oxidative polymerization of 4‐phenoxyphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane)copper(II) halogeno complex [Cu(tacn)X2] are described. With respect to the amount of the catalyst and the nature of the halide ion (X) of Cu(tacn)X2, the coupling selectivity hardly changed. The Cu(tacn) catalyst possessed a turnover number greater than 1860. As the temperature of the reaction and the polarity of the reaction solvent were elevated, the C O coupling at the o‐position increased, but the C C coupling was not involved. For the polymerization in toluene at 80 °C, poly(1,4‐phenylene oxide), obtained as a methanol‐insoluble part, showed the highest number‐average molecular weight of 4000 with a melting point (Tm) of 195 °C. Only a slight change in the coupling selectivity was observed in the presence or absence of hindered amines as the base. Surprisingly, however, the C O selectivity decreased from 100 to 24% with less hindered amines, indicating that the selectivity drastically changed from a preference for C O coupling to a preference for C C coupling. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4792–4804, 2000 相似文献
102.
p-(1-Methylcyclohexyloxy)styrene (PC6ST) was synthesized by acid catalyzed addition reaction of p-bromophenol with 1-methylcyclohexene, followed by Grignard coupling with vinyl bromide catalyzed by NiCl2(dppp). Radical polymerization of PC6ST in the presence or absence of TEMPO afforded poly(PC6ST) with narrow molecular weight distribution without the elimination of the protective group. The obtained poly(PC6ST) showed a higher deprotection ability in response to external stimulation such as an acid compared with poly(p-tert-butoxystyrene). 相似文献
103.
Hideyuki Itoh Atsushi Kameyama Tadatomi Nishikubo 《Journal of polymer science. Part A, Polymer chemistry》1997,35(15):3217-3225
Silicon-containing divinyl ether monomers were synthesized by the addition reaction of glycidyl vinyl ether ( 1 ) with various silyl dichlorides using tetra-n-butylammonium bromide (TBAB) as a catalyst. The reaction of 1 with diphenyl dichlorosilane gave bis-[1-(chloromethyl)-2-(vinyloxy)-ethyl]diphenyl silane ( 3a ) in 89% yield. Polycondensations of 3a with terephthalic acid were also carried out using 1,8-Diazabicyclo[5.4.0]-7-undecene (DBU) to afford silicon-containing polyfunctional vinyl ether oligomers ( 5 ). A multifunctional Si-monomer with both vinyl ether and methacrylate groups ( 7 ) was prepared by the reaction of 3a with potassium methacrylate using TBAB as a phase transfer catalyst. Photoinitiated cationic polymerizations of these vinyl ether compounds proceeded rapidly using the sulfonium salt, bis-[4-(diphenyl-sulfonio)phenyl]sulfide-bis-hexafluorophoshate (DPSP), as the cationic photoinitiator in neat mixtures upon UV irradiation. Multifunctional monomer 7 with both vinyl ether and methacrylate groups showed “hybrid curing properties” using both DPSP and the radical photoinitiator, 2,4,6-trimethylbenzoyl diphenylphoshine oxide (TPO). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3217–3225, 1997 相似文献
104.
Shin‐ichiro Shoda Masaya Fujita Chakapan Lohavisavapanichi Yoshinori Misawa Koushin Ushizaki Yukiko Tawata Mao Kuriyama Michinari Kohri Hideyuki Kuwata Takeshi Watanabe 《Helvetica chimica acta》2002,85(11):3919-3936
A novel strategy for the regio‐ and stereoselective synthesis by two enzymatic steps of oligosaccharides having an N‐acetylglucosamine unit at the nonreducing end was developed. The first step involves a chitinase‐catalyzed highly selective β‐N‐acetyllactosamination of an oligosaccharide acceptor with a 4,5‐dihydrooxazole derivative of N‐acetyllactosamine as the glycosyl donor. The usage of a transition‐state‐analogue substrate for the chitinase under basic conditions allows the reaction to proceed only in the synthetic direction while suppressing hydrolysis of the product in aqueous media. Several chitinase mutants also catalyzed the glycosylation efficiently under neutral conditions. The second step is a regioselective cleavage of the glycosidic bond between the terminal galactose unit and the adjacent N‐acetylglucosamine unit by the action of a β‐galactosidase. This constitutes a very useful method to add an N‐acetylglucosamine unit to the nonreducing end of chito‐ and cello‐oligosaccharide derivatives in a regio‐ and stereoselective manner. 相似文献
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108.
Zhigang Zhu Arunabhiram Chutia Hideyuki Tsuboi Nozomu Hatakeyama Hiromitsu Takaba Momoji Kubo 《Journal of Physics and Chemistry of Solids》2009,70(9):1248-258
A theoretical study on Ru-doped rutile SnO2(1 1 0) surface has been carried out by means of periodic density functional theory (DFT) at generalized gradient approximation (GGA-RPBE) level with a periodic supercell approach. Electronic structure analysis was performed based on the band structure and partial density of states. The results provide evidence that the electronic structures of SnO2(1 1 0) surface are modified by the surface Ru dopant, in which Ru 4d orbital are located at the edge of the band gap region. It is demonstrated that molecular oxygen adsorption characteristics on stoichiometric SnO2(1 1 0) surface are changed from endothermic to exothermic due to the existence of surface Ru dopant. The dissociative adsorption of molecular oxygen on the Ru5c/SnO2(1 1 0) surface is exothermic, which indicates that Ru could act as an active site to increase the oxygen atom species on SnO2(1 1 0) surface. Our present study reveals that the Ru dopant on surface is playing both electronic and chemical role in promoting the SnO2 gas-sensing property. 相似文献
109.
Makoto Yoshimoto Hideyuki Sakamoto Hiroshi Shirakami 《Colloids and surfaces. B, Biointerfaces》2009,69(2):281-287
Tetrameric bovine liver catalase (BLC) is unstable because of its dissociation into subunits at low enzyme concentrations and the conformational change of the subunits at high temperatures. In this work, for stabilization of BLC, the enzyme was covalently conjugated with liposome membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-glutaryl (NGPE). The NGPE, which was responsible for the BLC/membrane coupling, was altered from 0.05 to 0.2 in its liposomal mole fraction fG. The catalase-conjugated liposome (CCL) with fG of 0.15 showed the maximum number of the conjugated BLC molecules of 28 per liposome. The reactivity of CCLs to H2O2 was as high as that of free BLC at 25 °C in Tris–HCl buffer of pH 7.4. Among the CCLs, the catalyst with fG of 0.15 was the most stable at 55 °C in its enzyme activity in the buffer because the appropriate number of BLC/liposome covalent bonding prevented the dissociation-induced enzyme deactivation. Furthermore, the CCL showed much higher stability at 55 °C than the free BLC/enzyme-free liposome mixture and free BLC at the low BLC concentration of 340 ng/mL. This was because BLC in the CCL was located in the vicinity of the host membrane regardless of the catalyst concentration, which could induce the effective stabilization effect of the membrane on the enzyme tertiary structure as indicated by the intrinsic tryptophan fluorescence analysis. The results obtained demonstrate the high structural stability of BLC in the CCL system, which was derived from the covalent bonding and interaction between BLC and liposomes. 相似文献
110.
A chelate resin immobilizing carboxymethylated pentaethylenehexamine (CM-PEHA resin) was prepared, and the potential for the separation and preconcentration of trace elements in water samples was evaluated through the adsorption/elution test for 62 elements. The CM-PEHA resin could quantitatively recover various elements, including Ag, Cd, Co, Cu, Fe, Ni, Pb, Ti, U, and Zn, and rare earth elements over a wide pH range, and also Mn at pH above 5 and V and Mo at pH below 7. This resin could also effectively remove major elements, such as alkali and alkaline earth elements, under acidic and neutral conditions. Solid phase extraction using the CM-PEHA resin was applicable to the determination of 10 trace elements, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn, in certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and treated wastewater and all elements except for Mn in surface seawater using inductively coupled plasma atomic emission spectrometry. The detection limits, defined as 3 times the standard deviation for the procedural blank using 500 mL of purified water (50-fold preconcentration, n = 8), ranged from 0.003 μg L−1 (Mn) to 0.28 μg L−1 (Zn) as the concentration in 500 mL of solution. 相似文献