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排序方式: 共有671条查询结果,搜索用时 15 毫秒
661.
Morohashi I Sakamoto T Sotobayashi H Kawanishi T Hosako I Tsuchiya M 《Optics letters》2008,33(11):1192-1194
By combining a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG) with a dispersion-flattened dispersion-decreasing fiber, femtosecond pulses have been generated from a cw light. Near-Fourier-transform-limit picosecond pulses generated from the MZ-FCG were compressed into femtosecond order by pulse compression. Our system enables flexible tuning of the repetition rate and pulse width, because those depend on the driving signal of the MZ-FCG. Pulse trains of 200 fs width were continuously and stably generated without mode hopping, with a repetition rate range from 5 to 17 GHz. Our system consists of a modulator and compression fiber; thus, the configuration is simpler and more stable. 相似文献
662.
663.
Takuma Watabe Prof. Hideyuki Otsuka 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216469
We report a novel and versatile approach to achieving swelling-induced mechanochemistry using a multinetwork (MN) strategy that enables polymer networks to repeatedly swell with monomers and solvents. The isotropic expansion of the first network (FN) provides sufficient force to drive the mechanochemical scission of a radical-based mechanophore, difluorenylsuccinonitrile (DFSN). Although prompt recombination generally occurs in such highly mobile environments, the resulting pink radicals are kinetically stabilized in the gels, probably due to limited diffusion in the extended polymer chains. Moreover, the DFSN embedded in the isotropically strained chain exhibits increased thermal reactivity, which can be reasonably explained by an entropic contribution of the FN to the dissociation. The utility of the MN polymers is demonstrated not only in terms of swelling-force-induced network modification, but also in the context of tunable reactivity of the dissociative unit through proper design of the hierarchical network architecture. 相似文献
664.
665.
Hideyuki Kaneko Shingo Matsuo Nobuo Kawahara Junji Saito Tomoaki Matsugi Norio Kashiwa 《Macromolecular Symposia》2007,260(1):9-14
Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment. 相似文献
666.
Hideyuki Higashimura Kiyoshi Fujisawa Yoshihiko Moro‐oka Shuhei Namekawa Masaaki Kubota Akinobu Shiga Hiroshi Uyama Shiro Kobayashi 《Macromolecular rapid communications》2000,21(16):1121-1124
New heat‐reversibly crystalline poly‐(alkylated phenylene oxide)s are described. the oxidative polymerization of 2,5‐dimethylphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane) copper dichloride produced poly(2,5‐dimethyl‐1,4‐phenylene oxide), which showed heat‐reversible crystallinity with a high melting point at ca. 300°C, although the isomeric polymer, poly(2,6‐dimethyl‐1,4‐phenylene oxide), never recrystallizes once melted. The polymerization of 2,5‐diethylphenol and 2,5‐dipropylphenol gave the polymers consisting of 1,4‐phenylene oxide units; the latter polymer possessed heat‐reversible crystallinity, however, the former one did not. 相似文献
667.
668.
669.
Jun-ichi Kadokawa Yasuhiro Iwasaki Hideyuki Tagaya 《Macromolecular rapid communications》2002,23(13):757-760
Ring-opening polymerization of ethylene carbonate in the presence of ionic liquids, 1-butyl-3-methylimidazolium chloroaluminate melt and 1-butyl-3-methylimidazolium chlorostannate melt, has been investigated. Polymerization takes place accompanied with decarboxylation even at temperatures below 100°C under the reaction conditions selected to give poly(ethylene ether-carbonate)s. 相似文献
670.