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101.
102.
Koji Takagi Hiroki Kakiuchi Yasuo Yuki Masato Suzuki 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4786-4794
The synthesis and optical properties of polymers bearing the repeating unit of terfluorene and various organosilicon groups were investigated. Polymers with high molecular weight and good solubility could be obtained by Suzuki coupling polymerization from silylene‐containing fluorene‐based dibromo monomers and 9,9‐dihexylfluorene‐2,7‐bis(trimethyleneborate). From UV spectra of polymers bearing acyclic silylene bridge, the organosilicon units not only interrupted a π‐conjugation but also contributed to an electronic communication between connected fluorenes. The emission maximum wavelengths (ca. 400 nm) blue‐shifted when compared with that of polyfluorene (418 nm) and the fluorescence quantum yields were considerably high (>0.82) in the CHCl3 solution. On the other hand, rather broad emission was observed at 480 nm and the fluorescence quantum yield was quite low (0.004) in the solution‐state PL spectrum of tetraphenylsilole‐containing polymer. The polymer emitted visible green light in the spin‐coated film. The fluorescence peak intensity at 486 nm gradually decreased when the film was illuminated with the UV light of 359 nm in air. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4786–4794, 2007 相似文献
103.
Highly efficient processes for fine particle formation of metal alloys and metal oxides were developed using a high-power laser. In these processes, laser light was used only for the ignition of a thermal chain reaction. This reaction was suppressed by adding inert gases, and the suppression effect was in the order C3H8 > C2H6 > CH4 > He > Ar > Xe. Oxygen accelerated the reaction because of the large exothermicity of the reaction of oxygen with methyl metal compounds. 相似文献
104.
Fukuji Higashi Masato Koshio 《Journal of polymer science. Part A, Polymer chemistry》2003,41(4):616-623
A two‐stage copolycondensation of a mixture of equal parts of isophthalic acid and terephthalic acid first with a′,b′‐dihydroxyacetophenone (a′,b′‐DHAP) and then with isomeric c′,d′‐DHAP was examined at 60 and 80 °C. A structurally selective reaction was observed. At 80 °C, the preformed oligomers from symmetrically substituted 2′,6′‐DHAP reacted better with similarly substituted 2′,6′‐ or 3′,5′‐DHAP to give the copolymers of significantly higher inherent viscosity values than from the reaction with asymmetrically substituted 2′,4′‐DHAP, whereas at 60 °C they did almost equally well with any c′,d′‐DHAP. Similarly, the reaction of oligomers from 2′,4′‐DHAP with asymmetrically substituted 2′,4′‐DHAP or 2,4‐dihydroxybenzophenone yielded better results than those from the reaction with 2′,6′‐ or 3′,5′‐DHAP at both temperatures. The copolycondensations with comonomers of the structure independent of DHAPs were not affected by the preformed oligomers from DHAPs. The results are discussed in terms of the distributions of resulting oligomers determined by gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 616–623, 2003 相似文献
105.
106.
A Strategy to Control the Reactivation of Frustrated Lewis Pairs from Shelf‐Stable Carbene Borane Complexes 下载免费PDF全文
Dr. Yoichi Hoshimoto Takuya Kinoshita Prof. Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2015,54(40):11666-11671
N‐Phosphine oxide substituted imidazolylidenes (PoxIms) have been synthesized and fully characterized. These species can undergo significant changes to the spatial environment surrounding their carbene center through rotation of the phosphine oxide moiety. Either classical Lewis adducts (CLAs) or frustrated Lewis pairs (FLPs) are thus formed with B(C6F5)3 depending on the orientation of the phosphine oxide group. A strategy to reactivate FLPs from CLAs by exploiting molecular motions that are responsive to external stimuli has therefore been developed. The reactivation conditions were successfully controlled by tuning the strain in the PoxIm–B(C6F5)3 complexes so that reactivation only occurred above ambient temperature. 相似文献
107.
108.
Shin-ichi Matsuoka Shintaro ShimakawaKoji Takagi Masato Suzuki 《Tetrahedron letters》2011,52(50):6835-6838
The head-to-tail dimerization of methacrolein via the conjugate addition of methanol is catalyzed by various organic bases, such as an amine, phosphine, and N-heterocyclic carbene, to give 2,4-dimethyl-2-methoxymethylpentane-1,5-dial in moderate yields. Based on the interpretation of the key intermediates by electrospray ionization mass spectrometry, we propose a reaction mechanism involving the initial conjugate addition of the organic bases to methacrolein to generate a zwitterionic base followed by the activation of methanol. 相似文献
109.
Masato HigashinoNaoko Ikeda Tetsuro ShinadaKazuhiko Sakaguchi Yasufumi Ohfune 《Tetrahedron letters》2011,52(3):422-425
A novel silyl group-directed anti-SN2′ reaction of allylic alcohols under Mitsunobu reaction conditions is described. The Mitsunobu reaction of α-hydroxy-α-alkenylsilanes with a TBS or TIPS group gave the anti-SN2′ product, in which regio- and stereochemical outcomes of the reaction depended on the steric bulkiness of the silyl group. 相似文献
110.
Masato Matsuda Taiji Yakushiji Kiyotaka Sakai 《Surface and interface analysis : SIA》2011,43(6):976-983
In Japan, hemodialyzers are usually sterilized by γ irradiation. However, the polymer materials used in the dialysis membrane, such as polysulfone (PSf) and poly(vinylpyrrolidone) (PVP), undergo crosslinking or degradation on exposure to γ radiation. In the present study, we prepared PSf/PVP films (PVP content, 0–50 wt%) and used atomic force microscopy (AFM) to perform nanoscale evaluations of the effect of γ irradiation (25 and 50 kGy) on the surface properties of wet PSf/PVP surfaces. Force‐curve measurements were used to evaluate the hardness of and fibrinogen adsorbability on the wet PSf/PVP surface; fibrinogen adsorbability on the wet PSf/PVP surface was evaluated using AFM probes with fibrinogen immobilized on the tips of the probes. At PVP levels greater than 5 wt%, the wet PSf/PVP film surface was completely covered with hydrated and swollen PVP particles. The surface hardness of the wet PSf/PVP films exposed to 25‐kGy γ irradiation greatly decreased with increasing PVP content, whereas the surface hardness of the wet PSf/PVP films exposed to 50‐kGy γ irradiation did not decrease significantly. At higher PVP levels, the reduction in the fibrinogen adsorbability on a wet PSf/PVP film exposed to 25‐kGy γ irradiation was more significant than that on a wet PSf/PVP film exposed to 50‐kGy γ irradiation. PVP particles on the wet PSf/PVP film surface exposed to 50‐kGy γ irradiation did not show significant hydration and swelling because the polymer materials PVP–PSf and PVP‐PVP in these membranes has undergone excessive crosslinking due to γ irradiation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献