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111.
Toru Doi Akira Akimoto Akikazu Matsumoto Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1996,34(3):367-373
Radical copolymerization of N-methylmaleimide (MeMI) as well as other N-alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the Rp and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher Rp and an alternating tendency compared with those in dioxane (rMeMI = 0.14, r1B = 0 in chloroform and rMeMI = 0.47, r1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (Tg) and excellent thermal stability, e.g., the Tg and the thermal decomposition temperature (Td) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the Tg and Td increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties. © 1996 John Wiley & Sons, Inc. 相似文献
112.
Yoshihiro Itoh Masamitsu Inoue Akira Hachimori 《Journal of polymer science. Part A, Polymer chemistry》1996,34(1):89-93
Alternating and random copolymers of 2-(9-carbazolyl)ethyl methacrylate with aromatic vinyl monomers were synthesized and their fluorescence properties were compared in good and poor solvents. Contraction of the polymer coils induced the hypochromic effect, i.e., the mutual interaction of the ground-state chromophores, but caused little quenching of their excited state. This is sharp in contrast with the vinyl-type of polymers, exhibiting large interactions in both the ground and excited states. Introduction of bulky groups on the comonomers in the alternating copolymers further suppressed these interactions. © 1996 John Wiley & Sons, Inc. 相似文献
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The electron spin resonance spectra of Mn2+ ions have been studied in GexTe100?x with x = 15, 17.5 and 20, and Ge20?xTe80Six with 0 ?x? 20. All samples are found to exhibit six hyperfine lines centered at g = 4.3 with hyperfine interaction constant A = 56 × 10?4cm?1. The g = 4.3 line is interpreted as being caused by Mn2+ ions incorporated in the amorphous network and surrounded by four Te atoms in an arrangement of orthorhombic symmetry. Some of the samples of GeTe show a g = 2.0 line. This line also appears after heat treatment in air at temperatures above the glass transition temperature. It is concluded that the g = 2.0 line is caused by Mn2+ ions in phase separated microcrystalline or concentrated regions of MnO in the glass. 相似文献
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