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61.
62.
Abstract The non-linear dielectric relaxation spectroscopy has been recently developed and applied to soft materials such as polymers. We have applied this new method to the S*C phases of some ferroelectric liquid crystals. Under a weak AC electric field, the original and third order harmonic frequency components of electric displacement are proportional to the first and third powers of the applied electric field, respectively. The linear spectrum obtained from the original frequency component shows the relaxation of Debye type and the third order non-linear spectrum shows the relaxation with an extended form of Debye type to the non-linear case. The third order non-linear dielectric increment is found to be negative, which implies that the dielectric non-linearity of the liquid crystal in the S*C phase is due to the saturation of molecular dipole moments induced by the applied electric field. The temperature dependence of the linear and third order non-linear spectra in the S*C phase are also studied. Both spectra do not change their forms much through the whole temperature range of the S*C phase. In the vicinity of the SA–S*C transition temperature, the critical behaviour is more remarkable in the third order spectrum than in the linear one. 相似文献
63.
Polymerizations of cyclooctene, 5-methyl, 5-chloro-, and 5-methoxycyclooctenes were studied. Cyclooctene (CO) and 5-methylcyclooctene (MCO) provided high polymers in 80% yield with the use of WCl6/AlEti.B Clu5 or WCl6/AlEtCl2 catalyst. 5-Chlorocyclooctene gave oligomer in 50% yield with WCl6/AlEt2Cl catalyst. Neither polymer nor oligomer was produced from 5-methoxycyclooctene. These polymers were found to be produced through a ring-opening mechanism. The ratio of cis to trans structure in poly(CO) and poly(MCO) was determined by measurements of the decoupled ′H-NMR spectrum. Poly(CO) containing more than 50% trans structure was a crystalline solid at room temperature, while the polymer containing 30% of trans structure did not crystallize at room temperature. Poly(MCO) was amorphous, regardless of the content of trans structure. Poly(CO) and poly(MCO) obtained with MoCU/AlEtaCl or MoCU/AlEtCb catalyst contained no carbon-carbon double bond, and a vinyl polymerization mechanism was expected for this system. 相似文献
64.
Shiro Matsumoto Yasuyuki Sugiyama Seizou Sakata Takayoshi Hayashi 《Liquid crystals》2013,40(5):649-655
Polymers containing droplets of liquid crystal smaller than 100 nm, which have good transparency and easily form films, were prepared under various conditions to evaluate their potential as electro-optic materials for waveguide-type devices. By varying the liquid crystal concentration and the strength of the UV irradiation causing photo-induced phase separation of the droplets, we were able to control the droplet size and density. We have clarified how the birefringence generated in an applied electric field, switching speed, and optical loss of light propagating in the film depend on droplet size and density. Polymer materials having a large electro-optic effect (δn = 0.001 at 8 V μm-1), low propagation loss (~2.5 dB cm-1), and fast response time (~10 μs) have been developed. 相似文献
65.
A series of liquid crystalline compounds having the difluoropropyleneoxy moiety (–OCF2C2H4–) as a linking group has been synthesized. The physical properties, i.e. dielectric anisotropy, birefringence, viscosity and phase transition temperatures, have been measured. This novel class of compounds shows a larger negative dielectric anisotropy than the corresponding compounds having a propyleneoxy (–OC3H6–) linking group. Their dielectric properties may be explained by the combined effect of fluorine atoms with large electron negativities and the electron donating feature of an oxygen atom substituted on the same carbon atom. The semi‐empirical quantum calculation method (AM1) also confirmed this dielectric behaviour of the difluoropropyleneoxy linkage group. 相似文献
66.
Nobutaka Yamaoka Kohei Sumida Itsuki Itani Hiroko Kubo Yusuke Ohnishi Sho Sekiguchi Dr. Toshifumi Dohi Prof. Dr. Yasuyuki Kita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):15004-15011
Metal‐free oxidative C? C coupling by using polyalkoxybenzene‐derived diaryliodonium(III) salts as both the oxidant and aryl source has been developed. These salts can induce single‐electron‐transfer (SET) oxidation to yield electron‐rich arenes and subsequently transfer the polyalkoxyphenyl group into in situ generated aromatic radical cations to produce biaryl products. The reaction is promoted by a Lewis acid that activates the iodonium salts. It has been revealed that the reactivity of the salts under acidic conditions is quite different to their known behavior under basic conditions. The reactivity preference of a series of iodonium salts in the SET oxidation and their ligand transfer abilities have been systematically investigated and the results are summarized in this report. 相似文献
67.
Synthesis,Crystal Packing,and Ambipolar Carrier Transport Property of Twisted Dibenzo[g,p]chrysenes 下载免费PDF全文
Dr. Yasuyuki Ueda Dr. Hayato Tsuji Dr. Hideyuki Tanaka Prof. Dr. Eiichi Nakamura 《化学:亚洲杂志》2014,9(6):1623-1628
A versatile method for the synthesis of dibenzo[g,p]chrysene (DBC) derivatives based on regio‐ and stereoselective stannyllithiation to diarylacetylenes is described. This method affords a variety of DBCs possessing both electron‐donating and electron‐withdrawing functional groups. These twisted molecules take brickwork packing structures in single crystals. Thus, ambipolar carrier transport properties with mobility values of up to 10?3 cm2 V?1 s?1 in the amorphous state were achieved. Functional groups on DBC frameworks are considered to increase carrier mobility through the enhancement of intermolecular interactions in the brickwork packing structures. 相似文献
68.
Facile Insertion of Carbon Dioxide into Cu2(μ‐H) Dinuclear Units Supported by Tetraphosphine Ligands 下载免费PDF全文
Kanako Nakamae Dr. Bunsho Kure Prof. Takayuki Nakajima Prof. Yasuyuki Ura Prof. Tomoaki Tanase 《化学:亚洲杂志》2014,9(11):3106-3110
Reactions of meso‐bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm) with CuI species in the presence of NaBH4 afforded di‐ and tetranuclear copper hydride complexes, [Cu2(μ‐H)(μ‐dpmppm)2]X ( 1 ) and [Cu4(μ‐H)2(μ4‐H)(μ‐dpmppm)2]X ( 2 ) (X=BF4, PF6). Complex 1 undergoes facile insertion of CO2 (1 atm) at room temperature, leading to a formate‐bridged dicopper complex [Cu2(μ‐HCOO)(dpmppm)2]X ( 3 ). The experimental and DFT theoretical studies clearly demonstrate that CO2 insertion into the Cu2(μ‐H) unit occurred with the flexible dicopper platform. Complex 2 also undergoes CO2 insertion to give a formate‐bridged complex, [Cu4(μ‐HCOO)3(dpmppm)2]X, during which the square Cu4 framework opened up to a linear tetranuclear chain. 相似文献
69.
Jinhua Hong Shunsuke Kobayashi Akihide Kuwabara Yumi H. Ikuhara Yasuyuki Fujiwara Yuichi Ikuhara 《Molecules (Basel, Switzerland)》2021,26(12)
Solid electrolytes, such as perovskite Li3xLa2/1−xTiO3, LixLa(1−x)/3NbO3 and garnet Li7La3Zr2O12 ceramic oxides, have attracted extensive attention in lithium-ion battery research due to their good chemical stability and the improvability of their ionic conductivity with great potential in solid electrolyte battery applications. These solid oxides eliminate safety issues and cycling instability, which are common challenges in the current commercial lithium-ion batteries based on organic liquid electrolytes. However, in practical applications, structural disorders such as point defects and grain boundaries play a dominating role in the ionic transport of these solid electrolytes, where defect engineering to tailor or improve the ionic conductive property is still seldom reported. Here, we demonstrate a defect engineering approach to alter the ionic conductive channels in LixLa(1−x)/3NbO3 (x = 0.1~0.13) electrolytes based on the rearrangements of La sites through a quenching process. The changes in the occupancy and interstitial defects of La ions lead to anisotropic modulation of ionic conductivity with the increase in quenching temperatures. Our trial in this work on the defect engineering of quenched electrolytes will offer opportunities to optimize ionic conductivity and benefit the solid electrolyte battery applications. 相似文献
70.
Formation of One‐Dimensional Helical Columns and Excimerlike Excited States by Racemic Quinoxaline‐Fused [7]Carbohelicenes in the Crystal 下载免费PDF全文
Dr. Hayato Sakai Sho Shinto Prof. Yasuyuki Araki Prof. Takehiko Wada Prof. Tomo Sakanoue Prof. Taishi Takenobu Prof. Taku Hasobe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):10099-10109
A series of quinoxaline‐fused [7]carbohelicenes (HeQu derivatives) was designed and synthesized to evaluate their structural and photophysical properties in the crystal state. The quinoxaline units were expected to enhance the light‐emitting properties and to control the packing structures in the crystal. The electrochemical and spectroscopic properties and excited‐state dynamics of these compounds were investigated in detail. The first oxidation potentials of HeQu derivatives are approximately the same as that of unsubstituted reference [7]carbohelicene (Heli), whereas their first reduction potentials are shifted to the positive by about 0.7 V. The steady‐state absorption, fluorescence, and circular dichroism spectra also became redshifted compared to those of Heli. The molecular orbitals and energy levels of the HOMO and LUMO states, calculated by DFT methods, support these trends. Moreover, the absolute fluorescence quantum yields of HeQu derivatives are about four times larger than that of Heli. The structural properties of the aggregated states were analyzed by single‐crystal analysis. Introduction of appropriate substituents (i.e., 4‐methoxyphenyl) in the HeQu unit enabled the construction of one‐dimensional helical columns of racemic HeQu derivatives in the crystal state. Helix formation is based on intracolumn π‐stacking between two neighboring [7]carbohelicenes and intercolumn CH ??? N interaction between a nitrogen atom of a quinoxaline unit and a hydrogen atom of a helicene unit. The time‐resolved fluorescence spectra of single crystals clearly showed an excimerlike delocalized excited state owing to the short distance between neighboring [7]carbohelicene units. 相似文献