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991.
992.
Palladium-catalyzed carbonylation of 3,5-dimethoxybenzyl chloride (13) with benzyl 7-hydroxyoctanoate (12) afforded benzyl 7-(3,5-dimethoxyphenylacetoxy)octanoate (6) in 70% yield, which is the precursor of Curvularin (4). The ester (12) was easily prepared from the butadiene telomer obtained by the palladium-catalyzed reaction of butadiene with acetic acid. 相似文献
993.
994.
995.
Peter Cirkel Takashi Kato Norihiro Mizoshita Henri Jagt Kenji Hanabusa 《Liquid crystals》2004,31(12):1649-1653
Liquid crystalline physical gels have been prepared in a super twisted nematic configuration. These gels show a remarkable increase in switching speed from the in field to out of field relaxation. We explore whether these gels might be used in fast passive matrix displays. 相似文献
996.
997.
Hiromu Saito Mamoru Takahashi Takashi Inoue 《Journal of Polymer Science.Polymer Physics》1988,26(8):1761-1768
Orientation relaxation of dissimilar chains in the molten miscible blends, poly(methyl methacrylate)/poly(vinylidene fluoride) and poly(methyl methacrylate)/poly(vinylidene fluoride-co-trifluoroethylene), were investigated by measuring (1) the change of infrared dichroic ratio with time after the uniaxial stretching of film specimens, (2) the shear stress relaxation spectrum, and (3) birefringence relaxation in shear. The dissimilar polymers showed an identical time variation of the normalized Hermans orientation function. The blend showed a relaxation spectrum with a single characteristic relaxation time τc, depending on the blend composition. The birefringence relaxed monotonically, remaining positive. These results suggest that the dissimilar polymers do not relax independently but cooperatively. This behavior may be induced by a constraint due to the specific interactions between the dissimilar polymers, e.g., weak hydrogen bonding. For the cooperative chain relaxation, a third power relationship was found; τc/τe vprop; (M/Me),3 where τe and Me are the relaxation time and molecular weight of entanglement strand, respectively, and M is the number average molecular weight in the blend. 相似文献
998.
Takashi Ishiwata Atsuto Tokunaga Tsutomu Shinzawa Ikuzo Tanaka 《Journal of Molecular Spectroscopy》1984,108(2):314-327
An optical-optical double-resonance technique has been applied to study the D(0u+) ion-pair state of Br2 in a one-photon resonant three-photon absorption. The OODR transition proceeds through the high vibrational level of the B3Π(0u+) state, which compromises a large Franck-Condon shift required for the excitation of Br2 from the X1Σg+ state to the D(0u+) state. Dunham parameters of the D(0u+) state, based on a global least-squares fit of 407 transitions (v′ = 0–16, J′ = 17–115), are Y00 = 49928.443(41), Y10 = 134.467(19), Y20 = ?8.71(27) × 10?2, Y30 = ?3.36(10) × 10?3, Y01 = 4.2382(15) × 10?2, Y11 = ?1.061(36) × 10?4, Y21 = ?2.00(27) × 10?6, and Y02 = ?1.93(11) × 10?8 for 79Br2 (all in cm?1, and 3σ in parentheses). The single rovibronic fluorescence spectrum of the D(0u+) state shows a transition terminating on the X1Σg+ ground state, and establishes the absolute v′ numbering on the basis of the Franck-Condon factor calculations. The v′ = 2 and 3 levels of the D(0u+) state are strongly perturbed due to the heterogeneous interaction with the 1u state correlating with the same ionic products of the D(0u+) state at the dissociation limit, . 相似文献
999.
1000.