摘要：
Liquid crystals (LCs) have already been widely used in reconfigurable microwave devices as an excellent phase change material for their electric tunable dielectric properties. An accurate value of complex permittivity on a given LCs is the most important parameter on designing microwave devices. In this paper, a novel method is proposed to realise a broadband permittivity measurement. On the basis of the theory of perturbation, it consisted of a double-ridge waveguide cavity and the given vector network analyser. In order to have a broadband measuring range and uniformly distribute operating frequency points, multi-mode double-ridged waveguide cavity is introduced to resonate at 11 operating modes (TE,n = 1,2, horizontal ellipsis , 11). Meanwhile, to suppress the undesired-modes effectively, several non-radiating slots are applied to keep the operating modes easily recognisable, so as to complete the broadband complex permittivity measurement in 5-40 GHz using only one cavity. Besides, another feature of this method is that the total-required sample is only about 0.02 mL because the sample loading area in the double-ridged waveguide cavity is perfectly designed very small. Therefore, several NLCs are measured, including a certain commercial mixture MM (Merck), and M1 similar to M7, as developed LC mixtures with large dielectric anisotropy and low microwave losses.
关键词：
Diffraction efficiency;Light diffraction;Liquid crystals;Nematic liquid crystals;Optical properties;Refractive index
摘要：
The structures of flexodomains, which are similar to optical gratings and can be controlled by the amplitude of applied voltage and temperature, were verified through polarizing microscopy and light diffraction techniques. The properties of the optical grating induced by a bent-core nematic liquid crystal in planar cells with varied cell gaps and pretilt angles were studied. The period of optical grating decreases with the increase in the amplitude of the applied voltage and pretilt angle. In addition, the period increases with the increase in cell gap and temperature. The period of optical grating has a linear relationship with temperature. The continuously adjustable period has the potential to become an important and extended application of optical grating.
作者机构：
[闻炎豪; 戴志群; 王震; 李潭; 张智勇; 关金涛] Department of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan, 430023, China;[彭增辉] State Key Laboratory of Applied Otticr, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, 130033, China
通讯机构：
[Zhang, Z.-Y.] D;Department of Chemistry and Environmental Engineering, Wuhan Polytechnic University, Wuhan, China
关键词：
嘧啶乙炔;高介电各向异性;近晶相态液晶;高光学各向异性;合成
摘要：
中心环外侧嘧啶环作为液晶分子的极性介晶基团，能有效增大分子的偶极矩和分子间的作用力，提高分子的介电各向异性，降低液晶的驱动电压，也有利于形成近晶相液晶态。本文试图以嘧啶乙炔为中心结构单元，以异硫氰基为端基，设计合成了嘧啶乙炔类异硫氰基液晶化合物（nBTM-NCS）系列共5个化合物；它们都经过IR、1H-NMR、13C-NMR和MS光谱对其分子结构鉴定，经过差热分析仪 (DSC)和偏光显微镜(POM)对其液晶性能进行检测。实验结果表明，所有化合物的分子结构均正确，具有近晶相态，其熔点较高并呈现奇偶效应；其光学各向异性达到0.45左右，介电常数21~24左右，可作为铁电液晶和聚合物分散液晶材料配方组分。 The pyrimidine ring outside of the rigid core ring of liquid crystal molecules used as a polar mesogenic group, can effectively increase the molecular dipole moment and intermolecular force, improve the dielectric anis-otropy of the compounds, reduce the driving voltage of the liquid crystal, and also favor to form some smec-tic phases. In this paper, where pyrimidine acetyleneisused as the central structural unit and isothiocyanide asthe end group, we could see that a series of liquid crystal compounds (nBTM-NCS) about five compounds were designed and synthesized. The molecular structure of all compounds were identified by IR, 1H-NMR, 13C-NMR and MS spectra, and their liquid crystal properties were measured by differential thermal analyzer (DSC) and polarizing microscope (POM).The experimental results show that all the compounds have the correct molecular structure and smectic phases. The melting point of the compounds is high and it shows a parity effect. Its optical anisotropy reaches about 0.45, and the dielectric constant is about 22 to 24. It can be used as the components for ferroelectric liquid crystals and polymer-dispersed liquid crystal materials.
通讯机构：
[Guan, Jin Tao] W;Wuhan Polytech Univ, Sch Chem & Environm Engn, Wuhan 430023, Hubei, Peoples R China.
摘要：
Two series of alkylimidazole-based phosphines were conveniently synthesized in one step from the corresponding alkylimidazole by selective deprotonation and quenching with chlorodiphenylphosphine. The novel ligands are easily tunable and exhibit good-to-excellent performance in the palladium-catalyzed Suzuki coupling reaction.
摘要：
ABSTRACT A series of 4ʹ-(4-alkyl-phenyl)-2ʹ,6ʹ-difluorotolane isothiocyanate liquid crystal (LC) compounds were synthesised, and their phase transitions and electrooptical properties were investigated. These compounds exhibit high birefringence, about 0.47–0.52. As the number of carbon atoms in the alkyl chains increases, these LC compounds can exhibit smectic phases. When these LCs were mixed into the commercial LCs, the birefringence values of LC mixtures become higher than pure commercial LCs, and the visco-elastic coefficients of five LC mixtures are very close to each other at every test temperature. The results of response properties indicate that the compounds with a tri-fluorine substitution and n-propyl end group possess better response performance than the others. These LC compounds are particularly attractive for achieving fast response times in LC optic devices. Graphical Abstract
摘要：
以2，5-二取代-1，3，4-噁二唑为中心核，酯基（-COO-）为桥键，直链烷基为末端基团，在单侧苯环侧位上引入氟原子，设计合成了3个新型不对称弯曲形液晶化合物8，9a和9b；并通过IR，1 H NMR，13 C NMR，19 F NMR和MS对其结构进行鉴定，经差热扫描仪（ DSC）和偏光显微镜（ POM）测定其液晶相态。结果表明：所有目标化合物的分子结构正确，都呈现向列相态，向列相态温度范围最宽达78℃；侧位单氟苯环结构化合物（8）的向列相温度范围没有二氟苯环结构（9）的宽。
作者机构：
[刘胜; 张智勇; 申烦; 戴志群; 黄江涛] Department of Chemistry and Environment Engineering, Wuhan Polytechnic University, Wuhan, 430023, China;[彭增辉] Changchun Institute of Optics Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, 130033, China
通讯机构：
[Zhang, Z.-Y.] D;Department of Chemistry and Environment Engineering, Wuhan Polytechnic University, Wuhan, China
作者：
Liang Liu;Xiao Ming Song;Jin Tao Guan;Zhi Yong Zhang;Ben Mei Wei
期刊：
Asian Journal of Chemistry,2015年27(6):2093-2095 ISSN：0970-7077
通讯作者：
Guan, J.T.
作者机构：
[Liu L.] School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, China;[Wei B.M.; Guan J.T.; Zhang Z.Y.; Song X.M.] School of Chemical and Environmental Engineering, Wuhan Polytechnic University, Wuhan, China
通讯机构：
[Guan, J.T.] S;School of Chemical and Environmental Engineering, Wuhan Polytechnic University, Wuhan, China
关键词：
Dppc+-PF6-;Heck coupling reaction;Recyclable
摘要：
An efficient PdCl2-Dppc+-PF6--[bmim][PF6] catalytic system has been developed for the Heck coupling reaction of various aryl iodides with olefins. The catalytic system allows the coupling reaction to proceed smoothly in excellent yields and can be recycled 5 times with minimal loss of activity.
