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931.
Hisaaki Kanetsuna Masaki Hasegawa Shigenobu Mitsuhashi Toshio Kurita Kanji Sasaki Katsuhiro Maeda Hiroko Obata Tatsuko Hatakeyama 《Journal of Polymer Science.Polymer Physics》1970,8(7):1027-1037
Poly-2,5-distyrylpyrazine (poly-DSP) was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and measurements of dynamic viscoelastic and electrical properties. From DTA and TGA studies it was confirmed that poly-DSP melts at 321°C and depolymerizes rapidly to the monomer at temperatures between 335°C and 345°C in helium. The polymer is affected by oxygen above 200°C. The E′ value from dynamic viscoelasticity measurements on amorphous film is 2 × 1011 dyne/cm2 at room temperature. It decrease abruptly in the temperature range 140–150°C; but the net decrease of E′ within this temperature range is relatively small. The electrical properties of amorphous poly-DSP are characterized by a small temperature dependence of the dielectric constant between room temperature and 100°C. The dielectric loss tangent was observed to be small, and the dc conductivity was extremely small. It is concluded that rotation of the phenyl branches in the polymer occurs above ?30°C and the glass transition occurs at about 150°C. These properties are discussed in some detail in relation to the polymer structure. 相似文献
932.
The structure of tomentin has been confirmed as 5-hydroxy-6,7-dimethoxycoumarin (2), the derived 3,3-dimethylallyl ether giving a para-Claisen rearrangement product. Relief of strain in the corresponding 1,1-dimethylallyl ether has been found to result in a novel regiospecific ortho-Claisen rearrangement occurring on silica at room temperature. The structure 18 of the stable ortho-dienone formed has been confirmed by conversion of the corresponding dehydrodienone (15), obtained from the rearrangement of tomentin 1,1-dimethylpropargyl ether, to alloxanthoxyletin (25). 相似文献
933.
934.
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936.
937.
A. Hasegawa 《Physics letters. A》1974,47(2):165-166
An exact solution of stationary propagating wave intensities is obtained for two waves which are interacting with particles. One of the wave intensity forms a rarefaction wave while the other forms a shock and both propagate at the same speed. 相似文献
938.
939.
Benzofuroxan 5 , upon irradiation using a high pressure mercury lamp with a Pyrex filter in acetonitrile containing a little water, afforded 1H-azepine-2,7-dione 6 . The initial stage of this reaction would be formation of a highly reactive intermediate possessing two nitrile oxide functions. On the other hand, when compound 5 was irradiated using a low pressure mercury lamp in acetonitrile containing a little water, it afforded 6H-furazano[4,5-c]carbazole 3-oxide 11 and compound 6 . The structure of compound 11 was determined by an X-ray structural analysis. In the presence of an aromatic hydrocarbon, the formation of compound 11 was decreased and that of compound 6 was increased. Mechanistic studies on the photoreaction suggest that the photosensitized formation of compound 6 with the aromatic hydrocarbon may be carried out by the reabsorption of the fluorescence of it near 365 nm and the presence of it may quench the formation of compound 11 . 相似文献
940.
Ryozo Hasegawa Yasuhiro Tanabe Masamichi Kobayashi Hiroyuki Tadokoro Akira Sawaoka Naoto Kawai 《Journal of Polymer Science.Polymer Physics》1970,8(7):1073-1087
A convenient pressure apparatus was designed for crystallization of high polymers under hydrostatic pressure up to 5000 atm. Melt crystallization as well as heat treatment under various temperatures and pressures was carried out on several polymers, and the effects of pressure on the molecular and crystal structures of the samples are discussed. Heat treatment of syndiotactic polypropylene under high pressure yields a new crystal modification rather than the previously known helix and planar zigzag modifications. Of the three modifications of poly(vinylidene fluoride), modification III was found as a high-pressure phase for specimens in the unoriented state, while modification I was obtained as the most stable one on heat treatment of oriented specimens under high pressure. Heat treatment under high pressure converts ordinary isotactic poly-4-methylpentene-1 with a lower density than the noncrystalline value, to a new crystal modification with higher density. As is reasonable, the dense modification is stable in a high-pressure range. For these three cases, the orientation of specimens was found to remain unchanged during the transitions, which must therefore occur in the solid state. 相似文献