Effects of Nematic Compounds with High Clearing Points on the Multiplexing Performance of Twisted Nematic Displays

The addition of nematic compounds with high clearing points (N_h) to multiplexable nematic liquid crystals decreases the temperature dependence of the threshold voltage of twisted nematic displays. This effect depends on the dielectric anisotropy of the nematic liquid crystals containing N_h, as well as on the increase in T _c. In the case of 4-n-butylphenyl 4'-(4”-butyibenzoyloxy) benzoate, the low threshold voltage was exceptionally compatible with a small temperature dependence of threshold voltage, and this result was attributed to the large temperature dependence of the dielectric anisotropy in comparison with that of nematic liquid crystals containing other N_h's.     

无水三氯化铝催化乙醇脱水反应制乙烯的实验研究

针对浓硫酸或五氧化二磷作催化剂的不足,该研究采用无水三氯化铝催化乙醇制乙烯,可使反应体系在120~130℃左右产生大量乙烯气体。同时从理论上探究了无水三氯化铝催化乙醇脱水的机理,并从教学演示实验的角度改进了反应装置,取得了较好的实验效果。     

Separation and purification of lanosterol,dihydrolanosterol, and cholesterol from lanolin by high‐performance counter‐current chromatography dual‐mode elution method

Lanosterol is a potential drug for cataracts treatment, which can reverse the aggregation of intracrystalline proteins. The low concentration in lanolin calls for high‐performance separation methods. In this study, a counter‐current chromatography dual‐mode elution method was developed for the first time to separate and purify lanosterol from hexane extract of lanolin after saponification, in which the column was first eluted with the lower phase as mobile phase in head‐to‐tail mode, followed by the upper phase in the tail‐to‐head mode. High purity of lanosterol, dihydrolanosterol, and cholesterol can be obtained simultaneously. A solvent system composed of n‐heptane/acetonitrile/ethyl acetate (5:5:1, v/v/v) was selected and optimized via partition coefficient determination. Compounds such as 111 mg lanosterol, 84 mg dihydrolanosterol, and 183 mg cholesterol with high purity of 99.77, 95.71, and 91.43%, respectively, analyzed by high‐performance liquid chromatography were obtained within 80 min from 700 mg crude extract from 1.78 g lanolin. The method was also used to improve the purity of commercial lanosterol product from 66.97 to above 99%. Counter‐current chromatography could serve as a potential and powerful technique for commercial production of highly pure lanosterol.     

乳酸配合物(NH4)2[Sr(C3H5O3)4]的晶体结构、Hirshfeld表面分析和溶液化学性质

合成了无水乳酸配合物(NH₄)₂[Sr(C₃H₅O₃)₄]。用X射线单晶衍射仪对该配合物的晶体结构进行了表征,确定了其组成、空间结构和配位方式。绘制了配合物的Hirshfeld表面和2D指纹图,揭示了分子间的相互作用以及该配合物具有多个配位位点和较强的配位活性。根据相关的晶体数据计算出了该配合物的晶格能及其对应阴离子的摩尔体积,计算得到该配合物的晶格能为2742.9 kJ·mol^-1。用等温环境反应-溶解量热计测量了该配合物在298 K超纯水溶剂中的溶解焓。根据Pitzer电解质溶液理论,在298 K下获得了该配合物的无限稀释摩尔溶解焓△_sH_m^∞和Pitzer参数,确定该配合物的△_sH_m^∞为(114.01±0.04) kJ·mol^-1。计算了该配合物的表观相对摩尔焓(^ΦL)以及不同浓度下溶质和溶剂的相对偏摩尔焓(L₁和L₂)。最后,根据晶格能和△_sH_m^∞设计了热化学循环,并计算出了阴离子的水合焓值。热重和微商热重曲线进一步揭示了该配合物的结构。     

溶剂热法合成无水NaBiO3多晶粉末

Anhydrous NaBiO₃ polycrystal powders have been prepared through a new process in which the alkoxides were used as precursors and the parent ROH as medium. The influences of precursors and medium for products were investigated. The reducibility of Bi(Ⅲ) in solvthermal process and the morphology of NaBiO₃ powders were studied.     

在离子液体中利用Perkin反应合成肉桂酸

肉桂酸(3-苯基-2-丙烯酸)是一种重要的有机化工原料和中间体,广泛应用于医药工业、香料工业和其它精细化工等领域。本研究用离子液体作溶剂,无水碳酸钾为碱催化剂,用Perkin法[1-4]合成了肉桂酸,产率最高可达80·8%。1实验部分1.1离子液体的合成离子液体的合成见文献[5],在500mL     

一种简便合成2-丁炔-1,4-二醇衍生物的新方法

由2-丁炔-1,4-二醇可以很方便地得到2-丁炔-1,4-二氯,这一试剂在有机合成中有着广泛的应用。而在其它条件相同的情况下,制备2-丁炔-1,4-二溴并未得到相应较好的结果。我们用无水苯为反应溶剂,以温和的 (PPh3)PBr2作为卤代试剂(冰浴下液溴逐滴滴入PPh3苯溶剂中当场生成)卤化2-丁炔-1,4-二醇,选择性合成得到2-丁炔-1,4-二溴衍生物。同时也实现了2-丁炔-1,4-二醋酸酯的合成。     

Thermal Behaviour of Anhydrous α-, β- and γ-Cyclodextrin at Low Temperature

Heat capacities of anhydrous -and -cyclodextrin were measured by adiabaticcalorimetry between 10 K and 300 K. The thermalbehaviour of the two compounds exhibits significantdifferences. -Cyclodextrin shows an anomalousexcess heat capacity in the entire region between 70 Kand 210 K. In the case of -cyclodextrin, anendothermic effect is observed at 240K. This effect isanalysed through the study of the correspondingentropy change and discussed in terms ofintramolecular organization.Using the known heat capacity values of anhydrous-CD, a comparative analysis has been developed.For each cyclodextrin, the average behaviour of abound -D-glucopyranose has been calculated andcompared. From a thermodynamic point of view, thedegree of organization of the dehydrated macrocycliccompounds could be expressed as-CD -CD -CD.     

甲醇脱氢制无水甲醛的高活性Ag-SiO_2-Al_2o_3催化剂

采用溶胶－凝胶法制备了甲醇直接脱氢制无水甲醛的新型高活性催化剂Ag- SiO_2-Al_2O_3，并考虑了银负载量、焙烧温度及反应温度等对催化剂活性的影响 。XRD结果表明，反应前观察不到银的晶相峰，反应后出现Ag(111)，Ag(200)，Ag (220)，Ag(311)及Ag(222)的特征银晶相峰，SEM结果与XRD吻合得很好。该种特异 结构的催化剂具有对甲醇直接脱氢制甲醛的优异性能，其甲醇转化率达到95.0%， 甲醛得率也高达81.2%，超过己有的文献报道。     

Anhydrous state proton conduction in sulfonated bisphenol a polyetherimide with 1H‐1,2,4 triazole as proton solvent

In this study, bisphenol A polyetherimide was sulfonated to various degrees (22, 48, and 62%) by trimethylsilylchlorosulfonate (TMSCS). Novel anhydrous proton conducting polyelectrolytes were prepared by the incorporation of 1H‐1,2,4‐triazole (Taz) as proton solvent in sulfonated polyetherimide (SPEI) matrix. The conductivity reached about 2 × 10^–3 S/cm at 80 °C and 10^–2 S/cm at 140 °C. The temperature dependence proton conductivity of the polyelectrolytes followed Arrhenius equation. The conductivity improved considerably at a temperature close to the triazole melting temperature in SPEI(X)H matrix. It was proposed that the high mobility of the triazolium ions (vehicle diffusion), in addition to structure diffusion, contribute to the high conductivity of these proton conducting electrolytes above the melting temperature of triazole. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2178–2187, 2009