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101.
Shinya Hamasaki Chie Sawauchi Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):617-623
A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)2? Cl/Ru(Ind)Cl(PPh3)2 initiating system in the presence of n‐Bu2NH as an additive [where (MMA)2? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (Mn's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (Mw/Mn) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (Mn ~ 105) and narrow MWD (Mw/Mn ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu3N, whereas n‐BuNH2 resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148 相似文献
102.
Kyung‐Youl Baek Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(12):1937-1944
A series of functionalized 2‐bromoisobutyrates and 2‐chloro‐2‐phenylacetates led to α‐end‐functionalized poly(methyl methacrylate)s in Ru(II)‐catalyzed living radical polymerization; the terminal functions included amine, hydroxyl, and amide. These initiators were effective in the presence of additives such as Al(Oi‐Pr)3 and n‐Bu3N. The chlorophenylacetate initiators especially coupled with the amine additive gave polymers with well‐controlled molecular weights (Mw/Mn = 1.2–1.3) and high end functionality (Fn ~ 1.0). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1937–1944, 2002 相似文献
103.
The reaction of 3-methyl-2-methylene-1,3-oxazolidine ( 1a ) and phenylisothiocyanate (PhNCS) gives 3-methyl-2-(phenylthiocarbamoyl)methylene-1,3-oxazolidine ( 3 ) whereas that of 2-isopropylidene-3-methyl-1,3-oxazolidine ( 1b ) and PhNCS gives 1:1 alternating copolymers. It is assumed that the reaction of 1b and PhNCS forms a zwitterionic intermediate ( 2b ), followed by the successive combination of 2b to give 1:1 alternating copolymers 4 and/or 5 . Consequently, it was demonstrated that the copolymerization of 1b and PhNCS proceeds via a zwitterionic mechanism with complete ring-opening to afford the 1:1 alternating copolymer 5 . 相似文献
104.
We developed a novel measurement method of the Donnan potential difference at a charged membrane/salt solution interface. The method can measure the potential under the condition that the membrane charge density is much lower than the KCl concentration of the salt bridge. This method is very useful for obtaining the effective charge density of each layer of a bipolar membrane. The present experiments in a system of a negatively charged poly(vinyl alcohol) membrane and a single salt solution of KCl, NaCl, LiCl, CaCl2 and LaC3 revealed that the membrane effective charged density has the same value for all the ions. The experiments in mixed KCl and CaCl2 solution revealed that the potential in the system is governed mainly by the concentration of the counterion having the highest valence in the system. 相似文献
105.
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
106.
Xiaolei Wang Miho Emoto Atsushi Sugimoto Yusuke Miyake Kaori Itto Mitsuo Amasaka Shu Xu Hiroshi Hirata Hirotada Fujii Hirokazu Arimoto 《Tetrahedron letters》2014
A scalable synthetic route for 15N-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide (15N-TEEPONE) is described. This 15N-labeled nitroxide is suitable for electron paramagnetic resonance imaging of brain, and its higher sensitivity compared with that of its 14N-counterpart is an important advantage of the labeled derivative. 相似文献
107.
Makoto Obata Ryo Asato Kazunori Mitsuo Shiho Hirohara 《Journal of polymer science. Part A, Polymer chemistry》2014,52(7):963-972
Three CF3‐substituted methyl methacrylates (MMAs), 2,2,2‐trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFIPMA) and nonafluoro‐tert‐butyl methacrylate (NFTBMA), were polymerized by conventional radical polymerization to give oxygen‐permeable polymers for application in pressure‐sensitive paint (PSP). The radical copolymerizations of styrene with TFEMA, HFIPMA, or NFTBMA were carried out to examine the effect of CF3 groups on the polymerizability. The e values increased in the order of MMA (0.40) < TFEMA (0.76) < HFIPMA (1.19) < NFTBMA (1.31). The homopolymers of TFEMA, HFIPMA and NFTBMA (PTFEMA, PHFIPMA, and PNFTBM, respectively) were examined as polymers for use in PSP using 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II) (PtTFPP). The PSP consisting of PNFTBMA and PtTFPP exerted very high pressure sensitivity and very low temperature sensitivity. In the absence of oxygen, the temperature sensitivity decreased in the order of PTFEMA > PHFIPMA > PNFTBMA = PMMA, which corresponds to the order of glass transition temperatures (Tg). However, the activation energies of the overall process of the luminescence quenching by oxygen were found to be 16.8 (PMMA), 13.0 (PTFEMA), 6.8 (PHFIPMA), and 4.3 kJ mol?1 (PNFTBMA). Therefore, the low temperature sensitivity of PNFTBMA was attributed to its high degree of substitution with CF3 groups and to its relatively high Tg value. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 963–972 相似文献
108.
Dr. Shintaro Ishida Dr. Takashi Abe Dr. Fumiya Hirakawa Tomoyuki Kosai Katsuhiro Sato Prof. Dr. Mitsuo Kira Prof. Dr. Takeaki Iwamoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15100-15103
A persistent dialkylsilanone was synthesized by the dehydrobromination of a dialkylbromosilanol with tris(trimethylsilyl)silyl potassium in solution at ?80 °C: It was characterized by NMR and IR spectroscopy, and was tested in several reactions. In 29Si NMR spectrum in [D8]toluene, the signal due to the unsaturated silicon nuclei was observed at 128.7 ppm. Reactions of the dialkylsilanone with water and mesitonitrile oxide gave a silanediol and a [2+3] cycloadduct, respectively. The silanone remains intact in [D8]toluene below ?80 °C for at least two days, while it undergoes unprecedented isomerization to give a siloxysilene by means of 1,3‐silyl migration at higher temperatures. 相似文献
109.
Meiser P Weissman KJ Bode HB Krug D Dickschat JS Sandmann A Müller R 《Chemistry & biology》2008,15(8):771-781
The DKxanthenes are a family of yellow pigments which play a critical role in myxobacterial development. Thirteen unique structures from Myxococcus xanthus DK1622 differ in the length of their characteristic polyene functionality, as well as the extent of methyl branching. We aimed to understand the mechanistic basis for this "molecular promiscuity" by analyzing the gene cluster in DK1622, and comparing it to the DKxanthene biosynthetic locus in a second myxobacterium, Stigmatella aurantiaca DW4/3-1, which produces a more limited range of compounds. While the core biosynthetic machinery is highly conserved, M. xanthus contains a putative asparagine hydroxylase function which is not present in S. aurantiaca. This observation accounts, in part, for the significantly larger metabolite family in M. xanthus. Detailed analysis of the encoded hybrid polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS) assembly line provides direct evidence for the mechanism underlying the variable polyene length and the observed pattern of methyl functionalities. 相似文献
110.
Noboru Sato Yuichi Funato Yasuyuki Fukushima Takeshi Momose Mitsuo Koshi Yukihiro Shimogaki 《国际化学动力学杂志》2020,52(6):359-367
We established a gas-phase, elementary reaction model for chemical vapor deposition of silicon carbide from methyltrichlorosilane (MTS) and H2, based on the model developed at Iowa State University (ISU). The ISU model did not reproduce our experimental results, decomposition behavior of MTS in the gas phase in an environment with H2. Therefore, we made several modifications to the ISU model. Of the reactions included in existing models, 236 were lacking in the ISU model, and thus were added to the model. In addition, we modified the rate constants of the unimolecular reactions and the recombination reactions, which were treated as a high-pressure limit in the ISU model, into pressure-dependent rate expressions based on the previous reports (to yield the ISU+ model), for example, H2(+M) → H + H(+M), but decomposition behavior remained poorly reproducible. To incorporate the pressure dependencies of unimolecular decomposition rate constants, and to increase the accuracies of these constants, we recalculated the rate constants of five unimolecular decomposition reactions of MTS using the Rice-Ramsperger-Kassel-Marcus method at the CBS-QB3 level. These chemistries were added to the ISU+ model to yield the UT2014 model. The UT2014 model reproduced overall MTS decomposition. From the results of our model, we confirmed that MTS mainly decomposes into CH3 and SiCl3 at the temperature around 1000°C as reported in the several studies. 相似文献