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71.
Synthesis and healing properties of poly(arylether sulfone)–poly(alkylthioether) multiblock copolymers containing disulfide bonds
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Takayoshi Akiyama Akira Ushio Yoshitaka Itoh Yuya Kawaguchi Kazuya Matsumoto Mitsutoshi Jikei 《Journal of polymer science. Part A, Polymer chemistry》2017,55(21):3545-3553
Thermoplastic elastomers composed of soft and hard segments are important elastic and processable synthetic polymers. The microphase‐separated soft domains show low glass transition temperature and possess sufficient chain mobility at room temperature. In this study, we report the synthesis and healing properties of multiblock copolymers containing disulfide bonds as dynamic covalent bonds. The multiblock copolymers composed of poly(arylether sulfone) and poly(alkylthioether) segments were synthesized by oxidative coupling polymerization of the corresponding thiol‐terminated oligomers. Atomic force microscopy phase images, differential scanning calorimetry, and dynamic mechanical analysis curves indicated the microphase‐separated morphology of the multiblock copolymer. Self‐healing properties of the polymer were evaluated by changes in the elongation at break of the cut/adhered samples. The elongation recovery increased with UV irradiation time, and the multiblock copolymer showed a 93% recovery after UV irradiation for 5 h. The healing efficiency induced by UV irradiation, determined by subtracting the recovery without UV irradiation, was calculated to be 51%. According to the UV spectra and solubility changes after UV irradiation, the main healing factor in this study was the crosslinking reactions caused by thiyl radicals generated from UV irradiation instead of disulfide exchange reactions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3545–3553 相似文献
72.
H. Tajima S. IkedaM. Matsuda N. HanasakiJi-Won Oh H. Akiyama 《Solid State Communications》2003,126(10):579-581
We have fabricated a light-emitting diode from horse-heart cytochrome c and measured the electro-luminescence (EL) spectra. The spectra exhibit broad peaks around 530 and 690 nm, and a weak shoulder around 410 nm. The EL spectra are completely different from the photo-luminescence spectra previously reported. The appearance of the 690 nm emission band suggests the charge-transfer between the iron and the axial methionine ligand plays a crucial role in the electrical conduction in the cytochrome c film. 相似文献
73.
A. Takahashi D. Nakamura K. Tamaru T. Akiyama T. Okada 《Applied physics. B, Lasers and optics》2008,92(1):73-77
We describe a comparative study of the emission characteristics of debris from CO2 and Nd:YAG laser-produced tin plasmas for developing an extreme-ultraviolet (EUV) lithography light source. Tin (Sn) ions
and droplets emitted from a Sn plasma produced by a CO2 laser or an Nd:YAG laser were detected using Faraday cups and quartz crystal microbalance (QCM) detectors, respectively.
The droplets were also monitored by using silicon substrates as witness plates. The results showed higher ion kinetic energy
and lower particle emission for the CO2 laser than the Nd:YAG laser for the same laser energy (50 mJ). The average ion energy was 2.2 keV for the CO2 laser-produced plasma (LPP), and 0.6 keV for the Nd:YAG LPP. The debris accumulation of the CO2 LPP detected by the QCM detectors, however, was less than one fourth of that of the Nd:YAG LPP for the same laser energy.
Using ion energy data, the mirror lifetime is estimated for the CO2 and Nd:YAG lasers. In both cases, the upper limit of the number of shots was of the order of 106.
PACS 52.38.DX; 52.38.Ph; 52.38.Mf 相似文献
74.
Yusai Ito Naoki Sugimoto Takumi Akiyama Takeshi Yamazaki Kenichi Tanamoto 《Tetrahedron letters》2009,50(28):4084-11715
Cepaic acid was isolated as a novel xanthylium yellow pigment from the dried outer scales of the yellow onion Allium cepa Linne. Its structure was elucidated on the basis of ESI-MS and 2D NMR spectroscopy as a 9-carboxy-1,3,6,8-tetrahydroxyxanthylium, which suggests that cepaic acid and other yellow pigments in the dried outer skin of onion were formed by the nucleophilic reaction of phloroglucinol derived from quercetin, a flavonol in onion scales, by autoxidation to glyoxylic acid. To our knowledge, this is the first report of such a pigment in yellow onion. 相似文献
75.
Kenzi Akiyama 《Journal of Geometry》1994,51(1-2):1-12
In this paper, we characterize the Sherk plane as the only non-semifield translation plane of order 27 that admits an abelian group of order 27 in the translation complement. 相似文献
76.
An edge of a k-connected graph is said to be k-contractible if the contraction of the edge results in a k-connected graph. A k-connected graph with no k-contractible edge is called contraction critically k-connected. For k≥4, we prove that if both G and its complement Gˉ are contraction critically k-connected, then |V(G)|<k
5/3+4k
3/2.
Received: October, 2001 Final version received: September 18, 2002
AMS Classification: 05C40 相似文献
77.
Jin Akiyama Hiroshi Era Severino V. Gervacio Mamoru Watanabe 《Journal of Graph Theory》1989,13(5):571-573
Let the finite, simple, undirected graph G = (V(G), E(G)) be vertex-colored. Denote the distinct colors by 1,2,…,c. Let Vi be the set of all vertices colored j and let <Vi be the subgraph of G induced by Vi. The k-path chromatic number of G, denoted by χ(G; Pk), is the least number c of distinct colors with which V(G) can be colored such that each connected component of Vi is a path of order at most k, 1 ? i ? c. We obtain upper bounds for χ(G; Pk) and χ(G; P∞) for regular, planar, and outerplanar graphs. 相似文献
78.
Seong-Ju Kim Fuminori Akiyama Minoru Matsuda 《Journal of polymer science. Part A, Polymer chemistry》1987,25(6):1641-1651
Free radical copolymerization of sulfur dioxide with phenylacetylene (PA) in o-dichlorobenzene was studied in a range of temperatures from 30 to 80oC as a function of total monomer concentration ([SO2] + [PA]). PA content in the copolymers increases with decreasing total monomer concentration and increasing temperature. M w/M n becomes sharper with decreasing the total monomer concentration, but does not depend upon feed compositions which are changed keeping total monomer concentration constant at 2, 4, and 6 mol/L, respectively. These results strongly indicate the existence of depropagation. Thermal decomposition of the copolymers happens more easily than PA homopolymer and the carbon-centered free radicals are detected during the decomposition. Reactivity of ~ CH??(Ph) free radical (~ PA · ) is also discussed. 相似文献
79.
Eighteen kinds of pyrimido[5,4-d]pyrimidines together with several commercially available fluorescent compounds such as perylene, Rhodamine B, etc., were evaluated as the reagents for a peroxyoxalate chemiluminescence (CL) detection system by using a flow injection method. The peroxyoxalate CL reaction employed consists of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide, triethylamine, and a fluorophore. Under the conditions used, 2,6-bis[di-(2-hydroxyethyl)amino]-4,8- dipiperidinopyrimido[5,4-d]pyrimidine (Dipyridamole) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (1i) gave very intense chemiluminescence intensities which were larger than those of any other commercially available fluorescent compounds tested (e.g., 10 times larger than that of perylene). 相似文献
80.
We measured quantitative spectra of firefly (Photinus pyralis) bioluminescence in the presence of Zn2+ and other bivalent metal ions to investigate the effects of these metal ions on luciferin‐luciferase reaction. We studied the dependence of the quantum yield and spectrum on quantity and kind of bivalent metal ions. Adding various amounts of Mg2+, Mn2+ and Ca2+ produced virtually no change in the quantum yields or the spectra of bioluminescence. In contrast, increasing amounts of ions such as Zn2+ and Cd2+ decreased quantum yields and changed the bioluminescence color from yellow‐green to red. Quantitative analysis showed that the sensitivities of the quantum yield and color to various metal ions were in the order of Hg2+>Zn2+, Cd2+>Ni2+, Co2+, Fe2+≫Mg2+, Mn2+, Ca2+. We propose that the changes in quantum yield and spectrum caused by the metal ions are due to their effect on luciferase that surrounds oxyluciferin during its radioactive decay. We also found that having more metal ions accelerated bioluminescence reactions. The sensitivity of the reaction rate had no correlation with those of the quantum yield and spectrum. 相似文献