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61.
Masaki Kakiage Takeshi Yamanobe Tadashi Komoto Syozo Murakami Hiroki Uehara 《Journal of Polymer Science.Polymer Physics》2006,44(17):2455-2467
The effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene (UHMW‐PE) are discussed, based on a combination of in situ X‐ray measurement and stress–strain behavior. The sample films of metallocene‐ and Ziegler‐catalyzed UHMW‐PEs with a similar viscosity average MW of ~107 were prepared by compression molding at 180 °C. Stress profiles recorded at 160 °C above the melting temperature of 135 °C exhibited a plateau stress region for both films. The relative change in the intensities of the amorphous scattering recorded on the equator and on the meridian indicated the orientation of amorphous chains along the draw axis with increasing strain. However, there was a substantial difference in the subsequent crystallization into the hexagonal phase, reflecting the molecular characteristics, that is, MW distribution of each sample film. Rapid crystallization into the hexagonal phase occurred at the beginning point of the plateau stress region in melt‐drawing for metallocene‐catalyzed UHMW‐PE film. In contrast, gradual crystallization into the hexagonal phase occurred at the middle point of the plateau stress region for the Ziegler‐catalyzed film, suggesting an ease of chain slippage during drawing. These results demonstrate that the difference in the MW distribution due to the polymerization catalyst system dominates the phase development mechanism during melt‐drawing. The effect of the processing conditions, that is, the including strain rate and drawing temperature, on the melt‐drawing behavior is also discussed. The obtained results indicate that the traditional temperature–strain rate relationship is effective for transient crystallization in to the hexagonal phase during melt‐drawing, as well as for typically oriented crystallization during ultradrawing in the solid state. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2455–2467, 2006 相似文献
62.
Preparation of THP‐Ester‐Derived Pyridinium‐Type Salts and their Reactions with Various Nucleophiles
Prof. Dr. Hiromichi Fujioka Yutaka Minamitsuji Takahiro Moriya Kazuhisa Okamoto Ozora Kubo Tomoyo Matsushita Dr. Kenichi Murai 《化学:亚洲杂志》2012,7(8):1925-1933
Nucleophilic substitution at the anomeric positions of tetrahydropyranyl (THP) and related carbohydrate‐derived esters that proceeded through pyridinium‐type salt intermediates have been developed. Treatment of the 6‐substituted α‐acetoxy‐tetrahydropyrans with TMSOTf (TMS=trimethylsilyl) and 2‐substitutited pyridines, such as 2‐p‐tolylpyridine and 2‐methoxypyridine, led to the efficient generation of cis‐pyridinium‐type salts. These salts reacted with various nucleophiles, such as alcohols, azides, and organozinc reagents, to form nucleophilic‐substitution products. A characteristic feature of these processes was that they took place under mild conditions, which did not affect acid‐labile protecting groups. Furthermore, the reactions that employed azides and C‐nucleophiles generated 2,6‐trans products with high degrees of stereoselectivity. 相似文献
63.
I. Ando T. Sanefuji T. Yamanobe S. Watanabe G.A. Webb 《Journal of Molecular Liquids》1985,31(1):31-40
In order to investigate the effects of possible intermolecular interaction in methyl alcohol, we have measured the directly-bonded 13CH spin-spin coupling. 1JCH, in 13C enriched methyl alcohol under high pressures of up to 300 atm. The value of 1JCH is found to increase with increasing pressure. This experimental result is reasonably well interpreted by means of both finite perturbation INDO and sum-over-state INDO calculations. The effect of external pressure is incorporated into the calculations by means of a modified solvaton theory. 相似文献
64.
Kimihiro Kubo Takeshi Yamanobe Tadashi Komoto Isao Ando Toru Shiibashi 《Journal of Polymer Science.Polymer Physics》1989,27(4):929-937
High resolution 13C-NMR spectra of nylon 6 samples crystallized under various conditions and of a drawn sample were measured at room temperature by the cross polarization/magic angle spinning (CP/MAS) and pulse saturation transfer/magic angle spinning techniques. Additionally, 13C-NMR spectra of the drawn sample were measured at temperatures from 20 to 100°C by the CP/MAS technique and at 20 and 100°C by the low-power decoupling/magic angle spinning technique. The nylon 6 structure in the solid-state is discussed on the basis of these results. The solid-state 13C chemical shift data are used for reference in a study of conformation in solution. 相似文献
65.
Hisao Yoshida Tomoyo Hamajima Yuko Kato Junji Shibata Atsushi Satsuma Tadashi Hattori 《Research on Chemical Intermediates》2003,29(7-9):897-910
Photo-induced methane conversion was examined over Ag-MFI zeolite at room temperature. On the oxidized Ag-MFI zeolite, containing Ag+ exchanged cations, huge amounts of methane were adsorbed, even in the dark, and then converted to mainly ethane upon photo-irradiation without H2 production. It was revealed that Ag n + small clusters were formed at the expense of Ag+ ion during this photoreaction, and probably hydrogen would be stored as H+ on the ion-exchange sites instead of Ag+. On the other hand, the reduced sample containing larger clusters converted methane into alkene even without photo-irradiation. 相似文献
66.
Facile transformation of 7,14-dihydroxy-ent-kaurenes such as excisanin A (8), kamebanin (9), and kamebakaurin (10), which are abundant in plants of the genus Rabdosia species (Labiatae), to ent-abietanes was accomplished under the Mitsunobu reaction conditions. The δ, ε-unsaturated cis-fused α-methylene γ-lactones (17, 18, and 25) thus prepared showed a moderate cytotoxic activity on P388 murine leukemia cells. 相似文献
67.
Tris(p-bromophenyl)aminium hexachloroantimonate and perchlorate were utilized to promote the oxidative ring-opening reaction of cyclopropyl silyl ethers giving ring-expanded ketones. Exploration of salt quantity effect on the reaction allowed us to hypothesize that amine radical cation is regenerated through the oxidation of neutral amine by hexachloroantimonate anion. Based on this hypothesis, amine radical cation was initially generated by the treatment of parent amine with either antimony pentachloride or the mixture of silver perchlorate and molecular iodine, and subsequently reacted with same substrates. The in situ generated amine radical cation was found to promote the reaction, and the expected products were obtained in better yields than via use of the corresponding salt reagents. 相似文献
68.
36-W diode-pumped continuous-wave 1319-nm Nd:YAG ceramic laser 总被引:4,自引:0,他引:4
Lu J Lu J Murai T Takaichi K Uematsu T Xu J Ueda K Yagi H Yanagitani T Kaminskii AA 《Optics letters》2002,27(13):1120-1122
Continuous-wave output at 1319 nm was obtained from a laser-diode-pumped 1% ceramic Nd:YAG laser. As much as 36.3-W output was obtained under pump power of 290 W, with an optical-to-optical conversion efficiency of 12.5%. 相似文献
69.
We prepared an analogue of an antitumor bicyclic hexapeptide RA-VII whose amide configuration between residues 2 and 3 was fixed to cis by incorporating a triazole cis-amide bond surrogate. This analogue was shown, by NMR studies, to take almost the same conformation as that of the minor conformer of RA-VII. It showed no cytotoxic activity. 相似文献
70.
Mio Matsumura Aya Tanatani Tomoyo Kaneko Isao Azumaya Hyuma Masu Daisuke Hashizume Hiroyuki Kagechika Atsuya Muranaka Masanobu Uchiyama 《Tetrahedron》2013
We synthesized porphyrinylamide 4b and its N-methylated derivative 5b. Direct N-methylation of porphyrinylamides 4 proved unsuccessful, so 5b was obtained via N-methylation of 5-aminoporphyrin 10 with potassium hexamethyldisilazide. The secondary amide 4b exists in trans-amide form, while N-methylated amide 5b exists in the cis-amide form, both in solution and in the crystal. Thus, N-methylation of the amide bond of 4b resulted in trans to cis conformational alteration. 相似文献