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81.
Gen Kojima Hiroshi Wachi Kenkichi Ishigure Yoneho Tabata 《Journal of polymer science. Part A, Polymer chemistry》1976,14(6):1317-1330
High resolution 94-MHz 19F- and 100-MHz 1H-NMR spectra were measured on a series of tetrafluoroethylene (TFE)-propylene (P) copolymers having a range of composition (TFE/P molar ratio = 37/63–55/45) and polymerized at different temperatures (?23, 25 and 65°C). The spectra were analyzed in relation to copolymer compositions. The assignment of 19F resonance in terms of tetrads proposed previously was confirmed, and the tentative assignment of 1H resonances was proposed in terms of triads. The spectra thus interpreted revealed the sequence distribution of the copolymers. Copolymer compositions calculated from NMR spectra and elemental analysis agreed rather well with each other. Monomer reactivity ratios were calculated from the sequence distributions and compared with those obtained from the elemental analysis. It was observed that highly alternating copolymers are obtained in this system over a wide range of monomer composition at lower temperatures and that a deviation from alternancy increases slightly with rising polymerization temperature. 相似文献
82.
Yoichiro Iwase Koichi Kondo Kenji Kamada Koji Ohta 《Journal of polymer science. Part A, Polymer chemistry》2002,40(20):3534-3541
1,4‐Bis(4‐benzylpyridinium)butadiyne triflate was aggregated in dimethylformamide and spontaneously converted into the 1,4‐addition type of polydiacetylene. The polymerization took place in a dipolar aprotic solvent with a large dielectric constant that could enhance the aggregation of the ionic diacetylene salt through the electrostatic interaction. The molecular weight of the diacetylene was leveled off after 30 h at 80 °C to reach 1.5 × 104 (number‐average molecular weight) that consisted of the 1,4‐addition type of polydiacetylene similar to polydiacetylenes obtained in the conventional solid‐state polymerization. Electron spin resonance spectra revealed that diradicals were generated at the earlier state aggregation to give rise to a solution polymerization. The UV spectra also suggested the presence of the activated aggregation associated with the polymerization as well as the eximer emission spectra. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3534–3541, 2002 相似文献
83.
Tamás Veszprémi Yoshiya Harada Koichi Ohno Hideki Mutoh 《Journal of organometallic chemistry》1983,252(2):121-125
Penning ionization electron spectroscopy and CNDO/S calculations have been successfully applied to the analyses of the UV photoelectron spectra of 2- and 2,5-bistrimethylsilylthiophene and 2-t-butylthiophene. The relative intensities of the π type bands are greatly enhanced in the Penning spectra compared with those of the UV photoelectron spectra. 相似文献
84.
Hong-Ling Li Koichi Takahashi Yusuke Ujihira Mariko Ishiwatari Kurima Kobayashi Takahiko Iriyama Tokuzo Konishi 《Journal of Thermal Analysis and Calorimetry》1995,45(6):1359-1371
The Mössbauer spectra of Sm2Fe17Nx, prepared by the nitrogenation of Sm2Fe17 powders in an ammonia and hydrogen atmosphere, were observed at elevated temperatures to shed light on the thermal behavior of nitrogen in the compounds Sm2Fe17Nx. It was found that there were large differences in thermal behavior between the starting Sm2Fe17, crystalline Sm2Fe17Nx (x≈1.7) and amorphous Sm2Fe17Nx(x~7). The thermal decomposition behavior of Sm2Fe17N3.2, developed as one of the most promising hard magnetic materials, was found to be different under different atmospheres. 相似文献
85.
The infrared spectra of the water-nitrogen complexes trapped in argon matrices have been studied with Fourier transform infrared absorption spectroscopy. The absorption lines of the H20-N2 1:1, 1:2, 1:n, and 2:1 complexes have been confirmed on the basis of the concentration effects. In addition, we have observed a few lines and propose the assignments for the 2:2, 2:3, and 2:4 complexes in the nu1 symmetric stretching and nu2 bending regions of the proton-acceptor molecule, and in the bonded OH stretching region of the proton-donor molecule. The redshifts in the bonded OH stretching mode and blueshifts in the OH bending mode suggest that the hydrogen bonds in the (H2O)2-(N2)n complexes with n = 1-4 are strengthened by the cooperative effects compared to the pure H2O dimer. Two absorption bands due to the 3:n complexes are also observed near the bonded OH stretching region of the H2O trimer. 相似文献
86.
The effects of excipients on the protein stability during lyophilization as well as the storage stability of lyophilized bilirubin oxidase (BO) and beta-galactosidase (GA) formulations were studied using four polymer excipients: dextran, polyvinylalcohol (PVA), poly(acrylic acid) (PAA), and alpha, beta-poly(N-hydroxyethyl)-L-aspartamide (PHEA). Denaturation of BO and GA during lyophilization largely depended on the excipient used. Dextran appeared to cause severe damage to proteins, whereas PHEA protected proteins effectively from denaturation. Storage stability of BO and GA formulations also depended on the excipients, such that the formulations containing dextran and PAA were relatively unstable. Storage stability was improved by absorption of a small amount of water for all the formulations studied. Absorption of a larger amount of water, however, decreased the storage stability of the formulations containing PVA, PAA or PHEA. In contrast, the storage stability of formulations containing dextran did not decrease noticeably with increasing water. This may be because formulations containing dextran have a higher glass transition temperature than formulations containing PVA, PAA or PHEA when a large amount of water is absorbed. 相似文献
87.
Guan-Wu Wang Ting-Hu ZhangEr-Hong Hao Li-Juan JiaoYasujiro Murata Koichi Komatsu 《Tetrahedron》2003,59(1):55-60
The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C60(CH2N(CH3)CHR), R=H (4a), C6H5 (4b), p-NO2-C6H4 (4c), p-CH3O-C6H4 (4d), p-(CH3)2N-C6H4 (4e)) were obtained in moderate yields from reactions of C60 with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C60 with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C70 with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines. 相似文献
88.
Koichi Tokuda Tatsuro Gueshi Hiroaki Matsuda 《Journal of Electroanalytical Chemistry》1979,102(1):41-48
Faradaic, impedances at model electrodes partially covered with a photoresist layer have been studied theoretically and experimentally. Equations for the faradaic impedance are derived based on the theoretical model and approach described in Part I of this series of papers. Experimental data for the hexacyanoferrate system at various model electrodes give excellent agreement, with theoretical predictions for the diffusion impedance behavior, and the applicability of the derived equations to the estimation of the degree of coverage and the size of the active regions is confirmed. Furthermore, the application of such model electrodes to the kinetic study of electrode reactions with high heterogeneous charge transfer rates is suggested. 相似文献
89.
The infrared spectra of the carbon monoxide-water cluster as well as the CO monomer and dimer in an argon matrix at cryogenic temperatures have been reinvestigated on the basis of the isotope substitution experiment with 12CO and 13CO. Lines due to the CO-H2O 2-1 cluster in the matrix have been unambiguously identified in the CO and OH stretching regions. The isotope effect on the vibrational frequency of the cluster is observed in the CO stretching vibration but neither in the symmetric nor antisymmetric OH stretching vibrations. Each of the two vibrational lines due to the two CO vibrations of the CO-H2O 2-1 cluster is examined by comparing the expected spectral features at a 12CO/13CO ratio on a simulation with those observed experimentally. The migration of the trapped molecules (CO and H2O) in the matrix is discussed, in which the observed spectral change with the deposition temperature from 14 K to 30 K is explained. 相似文献
90.
[structure: see text] Alternate thiophene/furan oligomers having four and six heterocycles, i.e., oligo(thienylfuran) dimer and trimer 2 (n = 4 and 6), were newly synthesized by repetitive Stille coupling reactions. The structural, electronic, and optical properties of these oligomers were investigated by X-ray crystallography (for n = 4), cyclic voltammetry (CV), UV-vis and fluorescence spectroscopy, and DFT calculations, and the results were compared with those of corresponding oligothiophenes (1) and oligofurans (3). The inter-ring torsional energy profiles calculated for bithiophene 1 (n = 2), thienylfuran 2 (n = 2), and bifuran 3 (n = 2) at the B3LYP/6-31G(d) level indicated that the most stable conformers of 2 (n = 2) and 3 (n = 2) are fully coplanar with transoid structure while that of 1 (n = 2) is twisted with a dihedral angle of 158 degrees . In accord with this, X-ray crystallographic analysis of 2 (n = 4) revealed that the pi-conjugated system is nearly planar with the inter-ring C=C-C=C dihedral angles between the thiophene and furan rings of 173.6(7) degrees , -177.0(7) degrees , and 172.6(6) degrees . In the packing structure, these nearly planar molecules are arranged in a herringbone pattern. The CV on a series of oligo(thienylfuran)s 2 showed irreversible oxidation peaks at +0.90, +0.42, and +0.29 V vs Fc/Fc(+) for n = 2, 4, and 6, which were 0.15-0.18 V lower than those for corresponding oligothiophenes 1 and were closer to those for oligofurans 3. On the other hand, the UV-vis spectra of 2 showed the longest wavelength absorption to be almost identical with those of the corresponding 1, and more bathochromically shifted than those of the corresponding 3. The results of CV and UV-vis measurements were supported by DFT calculations (B3LYP/ 6-311+G(2d,p)//B3LYP/6-31G(d)). Thus, oligo(thienylfuran)s 2 have HOMOs which are higher than those of oligothiophenes 1 and close to those of 3, and HOMO-LUMO gaps which are close to those of 1 and smaller than those of 3. In fluorescence spectra, the quantum yield of 2 increased with elongation of the pi-system (n = 2 (3.5%), 4 (19%), 6 (24%)). 相似文献