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101.
Daisuke Nagai Asuka Fujii Masayoshi Tanaka Bungo Ochiai Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(6):1510-1521
Anionic polymerization of methacrylates under sterically confined environment in a spherical beads‐shaped networked polystyrene (NwPS) matrix is described. The initiator used herein is a samarium (Sm) (III) enolate, which was formed by treatment of 2‐bromoisobutylate immobilized in the side chain of NwPS with Sm (II) iodide. By using this NwPS‐bound initiator, polymerization of a series of methacrylates (=solid‐supported polymerization) was studied to find its two aspects: (1) In the early stages, the rate constant for each methacrylate was comparable to that for its conventional solution‐phase polymerization using a Sm (III) enolate, suggesting that methacrylate can be efficiently supplied to the propagating end by its free permeation without any interference by the networked structure of the matrix. (2) After the early stages, the rate constant decreased remarkably, implying that permeation of methacrylate was sterically interfered by the formed poly(methacrylate) that filled the confined space in NwPS, as supported by a SEM image of the resulting beads, of which pores were filled with the formed polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1510–1521, 2009 相似文献
102.
Infrared reflection absorption spectroscopy that used buried metal layer substrates (BML-IRRAS) and density functional cluster calculations were employed to investigate the water related oxidation reactions of 2H + H2O/Si(1 0 0)-(2 × 1), 2D + H2O/Si(1 0 0)-(2 × 1), and H2O + H/Si(1 0 0)-(2 × 1). In addition to the oxygen inserted coupled monohydrides, which were previously reported in the former reaction system, we report several other oxidized Si hydride species in our BML-IRRAS experiments. Three new pairs of vibrational bands are identified between 900 and 1000 cm−1. These vibrational frequencies were calculated using Si9 and Si10 cluster models that included all possible structures from zero to five oxygen insertions into the top layer silicon atoms using a B3LYP gradient corrected density functional method with a polarized 6-31G** basis set for all atoms. The three pairs of vibrational modes are assigned to the scissoring modes of adjacent and isolated SiH2 with zero, one, and two oxygen atoms inserted into the Si back bonds. All the other newly observed vibrational peaks related to Si oxidation are also assigned in this study. The Si-O stretching bands observed in the reaction 2D + H2O/Si(1 0 0)-(2 × 1) show an isotope effect, which suggests that in the system 2H + H2O/Si(1 0 0)-(2 × 1) also, hydrogen atom tunneling plays an important role for the insertion of oxygen atoms into Si back bonds that form oxidized adjacent dihydrides. 相似文献
103.
H. Nagai N. Oyama H. Yoshie A. Tsujimura 《Journal of magnetism and magnetic materials》1987,70(1-3):171-172
The educed Gd atoms in the X-structure (Th6Mn23-type) of Gd(Fe1−xMnx)2 were magnetically investigated by comparing with Gd6(Fe1−yMny)23 whose structure is Th6Mn23-type. The magnetic properties of Gd(Fe1−xMnx)2 (0.4≤x≤0.7) were observed to be quite similar to those of Gd6(Fe1−yMny)23 (0.4≤y≤0.7). 相似文献
104.
105.
Akira Tanaka Mitsuhiro Fukuda Hiroyuki Nagai Masayuki Shinohara Shigeharu Onogi 《Journal of Polymer Science.Polymer Physics》1989,27(11):2283-2293
A new apparatus was designed to investigate the dynamic viscoelastic properties of solid polymer materials in the nonlinear viscoelastic region. The apparatus was combined with a birefringence apparatus in such a way that birefringence could be measured simultaneously with stress under oscillatory deformation. The nonlinear viscoelastic behavior of bulk-crystallized high-density polyethylene films was examined. Nonlinearity of mechanical properties became evident around 30°C, while optical properties became markedly nonlinear around 50°C. The nonlinearity of viscoelastic properties changes very little when the films are swollen with tetrachloroethane. It is proposed that disruption of lamellae to crystallites in the drawing process is one of the most important causes of the nonlinear behavior of high-density polyethylene films. 相似文献
106.
In order to improve the stability of phenacyloxycarbamidomethyl (Pocam) group, a cysteine protecting group removable with zinc reduction, under acidic conditions, various alkyl substituents on the nitrogen atom of Pocam group were examined. As a result, attachment of an electron-withdrawing group improved the stability, and 2,2,2-trifluoroethyl (Tfe) group was most effective among four substituents tested. Tfe-Pocam group could be used in solid-phase peptide synthesis and peptide condensation reactions, and it was also useful for regioselective disulfide formation reactions. 相似文献
107.
Hidekazu Miyaji Junko Fujimoto Riho Mabuchi Moeno Okumura Shoichiro Goto Youtaro Honda 《Tetrahedron letters》2017,58(37):3623-3627
A novel molecular sensor using anthracene bearing two amidopyridines emits blue fluorescence in the presence of succinic acid and green fluorescence in the presence of malonic acid, and its fluorescence intensity increased upon binding. Using this molecular sensor, we succeeded in detecting the difference of one carbon atom between succinic acid and malonic acid with the naked-eye. Furthermore, when methylmalonic acid was dissolved in urine to provide a model system for methylmalonic aciduria, the fluorescence changed from blue to green, and methylmalonic acid was successfully detected with the naked-eye. 相似文献
108.
Tris(4-carboxylphenyl)-mono(N-methylimidazolyl)-substituted Zn porphyrin was synthesized as a precursor for a water-soluble supramolecular porphyrin dimer. The dimer formation was performed in a NaHCO3 aq solution (pH 8.4) and phosphate buffer solutions (pH 7.4-9.0). The split Soret bands of Zn porphyrin observed in the absorption spectra clearly showed self-organization to a special-pair type slipped cofacial dimer via metal coordination of imidazole even in water. 相似文献
109.
Yoshio Kitaoka Hidekazu Mukuda Shin-ichiro Tabata Akira Iyo 《Journal of Physics and Chemistry of Solids》2011,72(5):486-491
We reexamine the novel phase diagrams of antiferromagnetism (AFM) and high-Tc superconductivity (HTSC) for a disorder-free CuO2 plane based on an evaluation of local hole density (p) by site-selective Cu-NMR studies on multilayered copper oxides. Multilayered systems provide us with the opportunity to research the characteristics of the disorder-free CuO2 plane. The site-selective NMR is the best and the only tool used to extract layer-dependent characteristics. Consequently, we have concluded that the uniform mixing of AFM and SC is a general property inherent to a single CuO2 plane in an underdoped regime of HTSC. The T=0 phase diagram of AFM constructed here is in quantitative agreement with the theories in a strong correlation regime which is unchanged even with mobile holes. This Mott physics plays a vital role for mediating the Cooper pairs to make Tc of HTSC very high. By contrast, we address from extensive NMR studies on electron-doped iron-oxypnictides La1111 compounds that the increase in Tc is not due to the development of AFM spin fluctuations, but because the structural parameters, such as the bond angle α of the FeAs4 tetrahedron and the a-axis length, approach each optimum value. Based on these results, we propose that a stronger correlation in HTSC than in FeAs-based superconductors may make Tc higher significantly. 相似文献
110.
High-speed, wide-range wavelength scanning is demonstrated using a laser diode with an antireflection coating and an external cavity employing an acousto-optic deflector. The narrow spectral width of 0.2 nm observed in the experiment indicates the availability of a highly coherent laser beam. The scanning range of 15 nm under rapid modulation is confirmed in the prototype system. A tuning rate of more than 100 kHz is achieved without any mode hops. To the best of our knowledge, no such high-speed wavelength tuning based on an acousto-optical configuration has been demonstrated thus far. 相似文献