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排序方式: 共有178条查询结果,搜索用时 15 毫秒
71.
Takakazu Kojima Rikio Yokota Masakatsu Kochi Hirotaro Kambe 《Journal of Polymer Science.Polymer Physics》1980,18(8):1673-1683
Light scattering and viscometric studies have been carried out on dilute solutions of a polybenzimidazole in N,N-dimethylacetamide. The data, which span the molecular weight range 2.9 ≦ 10?4Mw ≦ 23.3, and the temperature range 290 ≦ T/K ≦343, yield the dependence of the mean-square radius of gyration 〈s2〉LS, the second virial coefficient A2, and the intrinsic viscosity [η] on molecular weight Mw and temperature. The unperturbed mean-square radius 〈s〉LS was calculated using experimental values of 〈s2〉LS and A2. It was found that excluded volume effects on 〈s2〉LS are very small. The unperturbed hydrodynamic chain dimension 〈s〉η was estimated by considering draining effects. A small value of the draining parameter was obtained. Analysis of the temperature dependence of A2 and [eta;] leads to the conclusion that this system approaches a lower theta temperature with increasing temperature. The steric factor σ = 〈s〉/〈s〉f, based on the value of 〈s〉f calculated for the polymer chain with free rotation, is nearly unity. Most of these properties can be interpreted in terms of long rotational units within the main chain. 相似文献
72.
73.
Otsuka H Takeda Y Hirata E Shinzato T Bando M 《Chemical & pharmaceutical bulletin》2004,52(5):591-596
The dimeric butenolides glochidiolide and isoglochidiolide, a new glucoside of a nitrogen-containing C(8) dimer, acuminaminoside, and glucosides of C(8) compounds, designated glochidacuminosides A-D, were isolated from the leaves of Glochidion acuminatum. The structures of glochidionolactone and acuminaminoside were determined by X-ray analyses, and those of the remaining C(8) glucosides by NMR spectroscopic analyses, chemical conversion, and a modified Mosher's method. 相似文献
74.
K. HIRAMATSUT. MATSUI T. MIYAKITAA. ITO T. TOKUYAMAY. OSADA T. YAMAMOTO 《Journal of sound and vibration》2002,250(1):139-144
Discriminant function values of psychosomatics and neurosis are calculated using the 12 scale scores of the Todai Health Index, a general health questionnaire, obtained in the survey done around the Kadena and Futenma U.S. airfields in Okinawa, Japan. The total number of answers available for the analysis is 6301. Factor analysis is applied to the 12 scale scores by means of the principal factor method, and Oblimin rotation is done because the factors extracted are considered likely to correlate with each other to a greater or lesser extent. The logistic regression analysis is made with the independent variables of discriminant function (DF) values and factor scores and with the dependent variables of Ldn, age (six levels), sex, occupation (four categories) and the interaction of age and sex. Results indicate that the odds ratio of the DF values regarding psychosomatic disorder and of the score of somatic factor have clear dose-response relationship. The odds ratios of the DF value of neurosis and of the score of the mental factor increase in the area where noise exposure is very intense. 相似文献
75.
Takayuki Iijima Masahiro Abe Take‐Aki Koizumi Atsushi Fukaya Kyohei Usami Kenichiro Kami Takakazu Yamamoto 《先进技术聚合物》2013,24(10):927-933
The reaction of 2,5‐diiodo‐1,4‐benzenedicarbonyl chloride, C6H2I2(COCl)2‐p, with 4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO‐ol) gave I–Ph(COO–TEMPO)2–I, Monomer‐1. Pd‐catalyzed polycondensation of Monomer‐1 with Me3Sn‐Th‐SnMe3 (2,5‐bis(trimethylstannyl)thiophene) and Bu3Sn–CH = CH–SnBu3 (1,2‐bis‐(tributylstannyl)ethylene) gave the corresponding π‐conjugated polymers, Polymer‐1 and Polymer‐2, respectively. Monomer‐1 was converted to a diethynyl compound, H–C ≡ C–Ph(COO–TEMPO)2–C ≡ C–H (Monomer‐1'), and Pd‐catalyzed polycondensation between Monomer‐1 and Monomer‐1' gave a π‐conjugated poly(arylene ethynylene) type polymer, Polymer‐3. According to the expansion of the π‐conjugation system by the polymerization, the UV–vis peaks of Monomer‐1 (λmax = 323 nm) and Monomer‐1' (327 nm) are shifted to longer wavelengths (λmax = 365 nm, 385 nm, and 396 nm for Polymer‐1, Polymer‐2, and Polymer‐3, respectively). Polymer‐1–Polymer‐3 showed ESR signals at about g = 2.01 with reasonable intensities. They are electrochemically active and showed a peak current anodic (oxidation) peak at about 0.9 V versus Ag/AgCl, which is reasonable for TEMPO polymers. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
76.
Takakazu Yamamoto Ban‐Lin Lee Hisashi Kokubo Hideo Kishida Keisuke Hirota Takeru Wakabayashi Hiroshi Okamoto 《Macromolecular rapid communications》2003,24(7):440-443
A new π‐conjugated charge‐transfer‐type copolymer of electron‐donating thiophene and electron‐accepting quinoxaline was prepared by organometallic polycondensation. The polymer was soluble in organic solvents such as tetrahydrofuran, and showed a UV‐vis peak at long wavelengths of 598 nm in chloroform and 629 nm in the film. Its film exhibited a χ(3) peak in the resonance region with a χ(3) value comparable to that of regioregular head‐to‐tail poly(3‐hexylthiophene‐2,5‐diyl).
77.
Qiang Fang Takakazu Yamamoto 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2686-2697
A novel photoluminescent polymer (PPyne) containing a 2‐pyrazoline unit in the molecular main chain was prepared (for the first time) by polycondensation between a 2‐pyrazoline monomer [an adduct of 2,6‐bis(4‐bromobenzylidene)cyclohexanone with phenylhydrazine] and 2,5‐dihexyloxy‐p‐phenylene diboric ester in the presence of Pd(PPh3)4. PPyne had a number‐average molecular weight of 7800 and a polydispersity index of 1.99 and showed good solubility in common organic solvents. In toluene PPyne exhibited an intrinsic viscosity [η] of 0.42 dL g?1 at 30 °C. The polymer was photoluminescent (PL) in both the chloroform solution and the solid state; the quantum yield of PL in the solution was 40%. In the two states, PPyne gave the same ultraviolet–visible (UV–vis) peak at 368 nm and the same PL peak at 512 nm. DSC traces indicated that PPyne had a melting temperature of 168 °C, and thermogravimetric analysis revealed that the polymer had good thermal stability with a 5 wt % loss temperature of 376 °C under N2. Electrochemical oxidation of PPyne started at about 0.5 V versus Ag/AgNO3 and gave a peak at 0.98 V versus Ag/AgNO3 with a color change of the film from yellow to black green. The color change was followed by UV–vis spectroscopy. The corresponding reduction peak appeared at 0.80 V versus Ag/AgNO3. Treatment of PPyne with HCl led to dehydrogenating transformation of the polymer to a new cross‐conjugated polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2686–2697, 2004 相似文献
78.
79.
Sanshiro Komiya Motonori Bundo Takakazu Yamamoto Akio Yamamoto 《Journal of organometallic chemistry》1979,174(3):343-354
Two types of dialkylcobalt(III) complexes containing the 2,2′-bipyridine ligand have been isolated as products of the reactions of tris(2,4-pentanedionato)cobalt(III) (Co(acac)3), 2,2′-bipyridine (bpy), and alkylaluminums in diethyl ether. When high Al/Co ratios (Al/Co > 7) were used, ionic complexes, dialkylbis(2,2′-bipyridine)cobalt(III) tetraalkylaluminates, [CoR2(bpy)2][AlR4] (R = CH3, C2H5) were obtained exclusively. Similar reactions at lower ratios (Al/Co - 1.5–2.0) gave neutral CoR2(acac)(bpy) (R = CH3, C2H5, n-C3H7, i-C3H7). These compounds were characterized by IR and NMR spectroscopy as well as by elemental analysis and chemical reactions. Molecular structural analysis of the cationic dimethylcobalt compound confirmed the cis configuration. Stepwise formation of [CoR2(bpy)2][AlR4] from Co(acac)3 is postulated and the mechanism of the alkylation reaction is discussed. 相似文献
80.
Awasthi K Mizoguchi M Iimori T Nakabayashi T Ohta N 《The journal of physical chemistry. A》2008,112(19):4432-4436
Magnetic field effects on the fluorescence spectrum and on the electrofluorescence spectrum (plots of the electric field-induced change in fluorescence intensity as a function of wavelength) have been examined in electron donor and acceptor pairs of N-ethylcarbazole (ECZ) and dimethyl terephthalate (DMTP) in polymer films at different ratios of donor/acceptor concentration. In the mixture having a high concentration of ECZ, electric field-induced quenching of the exciplex fluorescence originating from the photoinduced electron transfer becomes less efficient in the presence of a magnetic field. In the mixture having a low concentration of ECZ, on the other hand, no magnetic field effect was observed in the electrofluorescence spectrum, indicating that the hole carrier plays an important role in synergy effects of magnetic and electric field effects on exciplex fluorescence. In the absence of the applied electric field, the magnetic field does not affect either exciplex fluorescence with a peak at 450 nm or LE fluorescence emitted from the locally excited state of ECZ but enhances the broad emission with a peak at approximately 380 nm, probably assigned to the fluorescence of another type of exciplex between ECZ and DMTP. Thus, two kinds of magnetic field effects on fluorescence have been observed in a mixture of ECZ and DMTP in a polymer film. 相似文献