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191.
Various mixed liquid crystals containing crown ether‐cholesteryl liquid crystal, benzo‐15‐crown‐5‐COO‐C27H45 (B15C5‐COOCh), with various common cholesteric liquid crystals, e.g., cholesteryl chloride, cholesteryl benzoate and cholesteryl palmitate, were prepared and studied using polarizing microscopy and differential scanning calorimetry. Investigating the concentration effect of B15C5‐COOCh in mixed liquid crystals revealed that the addition of B15C5‐COOCh resulted in wider phase transition temperature ranges of these cholesteryl liquid crystals. The stability of these B15C5‐COOCh/cholesteryl mixed liquid crystals was studied using comprehensive graphic molecular modeling computer programs (Insight II and Discover) to calculate their molecular energy and stability energy. The effect of salts, e.g. Na+, Co3+, Y3+ and La3+, on the transition temperature range of the mixed liquid crystals was also investigated. The crown ether cholesteric liquid crystal B15C5‐COOCh was applied both as a surfactant and an ion transport carrier to transport metal ions through liquid membranes. Cholesteryl benzo‐15‐crown‐5 exhibited distinctive characteristics of a surfactant and the critical micellar concentration (CMC) of the surfactant was investigated by the pyrene fluorescence probe method. Cholesteryl benzo‐15‐crown‐5 was successfully applied as a good ion transport carrier (Ionophore) to transport various metal ions, e.g. Li+, Na+, La3+, Fe3+ and Co3+, through organic liquid membranes. The transport ability of the cholesteryl benzo‐15‐crown‐5 surfactant for these metal ions was in the order: Co3+ ≥ Li+ > Fe3+ > Na+ > La3+. 相似文献
192.
Bing Yang Dr. Soo‐Kang Kim Hai Xu Young‐Il Park Houyu Zhang Dr. Cheng Gu Fangzhong Shen Dr. Chunlei Wang Dandan Liu Xiaodong Liu Prof. Muddasir Hanif Shi Tang Weijun Li Feng Li Dr. Jiacong Shen Prof. Jong‐Wook Park Prof. Yuguang Ma Prof. 《Chemphyschem》2008,9(17):2601-2609
Herein, we describe the molecular electronic structure, optical, and charge‐transport properties of anthracene derivatives computationally using density functional theory to understand the factors responsible for the improved efficiency and stability of organic light‐emitting diodes (OLEDs) with triphenylamine (TPA)‐substituted anthracene derivatives. The high performance of OLEDs with TPA‐substituted anthracene is revealed to derive from three original features in comparison with aryl‐substituted anthracene derivatives: 1) the HOMO and LUMO are localized separately on TPA and anthracene moieties, respectively, which leads to better stability of the OLEDs due to the more stable cation of TPA under a hole majority‐carrier environment; 2) the more balanceable hole and electron transport together with the easier hole injection leads to a larger rate of hole–electron recombination, which corresponds to the higher electroluminescence efficiency; and 3) the increasing reorganization energy for both hole and electron transport and the higher HOMO energy level provide a stable potential well for hole trapping, and then trapped holes induce a built‐in electric field to prompt the balance of charge‐carrier injection. 相似文献
193.
L. Starannikova M. PilipenkoN. Belov Yu. YampolskiiM. Gringolts E. Finkelshtein 《Journal of membrane science》2008
Polymerization of norbornene bearing Si(CH3)3 groups in the five position with the opening of double bonds was performed. By accurate selection of the ratios catalyst/co-catalyst and monomer/catalyst the samples with increased molecular mass (about 400,000) were obtained. Transport parameters of this, addition type poly(trimethylsilyl norbornene) (PTMSN) were measured using the gas chromatographic and mass spectrometric methods for different gases (H2, He, O2, N2, CO2, CH4, C2H6, C3H8 and n-C4H10). Temperature dependence of the permeability coefficients (P) indicated that low activation energies of permeation (EP) and diffusion (ED) are characteristic for PTMSN. In some cases (CO2, C2H6) negative EP values were observed. Thermodynamics of vapor sorption in this polymer was studied using the inverse gas chromatography method. It was shown that PTMSN is characterized by very large solubility coefficients S similar to those of poly(trimethylsilyl propyne) (PTMSP). The comparison of the P, D, and S values of these highly permeable polymers showed that the greater permeability of PTMSP is determined by the larger D values. Application of different approaches for the determination of the size of microcavities in PTMSN indicated that this polymer is characterized by large size of microcavity (800–1200 ?3). 相似文献
194.
Xi Lu Huayang Wang Zhengting Cai Dacheng Feng 《International journal of quantum chemistry》2008,108(2):334-338
In the course of an extensive investigation aimed at understanding the detailed mechanism of a prototypical polyatomic reaction, several remarkable observations were uncovered. To interpret these findings, we surmise the existence of a reactive resonance in this polyatomic reaction. The concerned system is HO + CH4 → H2O + CH3, of which the partial potential energy surface is constructed by the coupling between vibrational models and reactive coordinates. Then we explain the formation mechanism of the reactive resonance state by the partial potential energy surface. Finally, we estimated the lifetime of the resonance state, and it is about 45fs. The study of the reactive resonance in a polyatomic reaction is more than just an extension from a typical atom + diatom reaction. As shown here, it holds great promise to disentangle the elusive intramolecular vibrational dynamics of the transient collision complex in the critical transition‐state region. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
195.
Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9Co0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane 下载免费PDF全文
Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9Co0.1O3 perovskite oxides as oxygen cartier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction. Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox re-action decreased over La0.8Sr0.2Fe0.9Co0.1O3 oxide, while LaFeO3 and Lao.sSro.2FeO3 exhibited excellent structural stability and continuous oxygen supply. 相似文献
196.
氧亲和力是血红蛋白氧载体非常重要的参数之一,但其高低还没有统一的认识,有一种理论认为低氧亲和力是造成高血压的原因。为了进一步研究氧亲和力与血压之间的关系,本文制备了两种低氧亲和力的血红蛋白氧载体。用高碘酸钠氧化棉子糖(高碘酸钠:棉籽糖=6:1,摩尔比),得到氧化均一的开环棉子糖;以其作为交联剂聚合脱氧猪血红蛋白,在聚合1 h得到了低氧亲和力(P50 = 43.1 torr)主要为分子内交联的64 kDa的血红蛋白,在聚合2 4 h得到了低氧亲和力(P50 = 51.5 torr)平均分子量为600 kDa的聚合血红蛋白;分别进行大鼠50%等容量换血实验,前者显著引起血压升高而后者血压平稳,证实高血压主要和64 kDa血红蛋白有关,低氧亲和力不是造成高血压的主要原因。 相似文献
197.
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199.
羟基磷灰石(HA)是人体和动物骨骼的主要无机矿物成分。近年来,因HA具有特殊的表面特性和理化性能,良好的生物相容性、生物活性和骨传导作用,制备各种形态的HA材料成为从事生物、医学和材料的科研人员的研究重点。本文首先介绍了HA微球的制备方法,重点讨论了以聚合物为软模板以及用各种球形材料作为硬模板合成HA微球的制备方法,列出了不同方法制备HA微球的直径、孔径、比表面等各种性能参数。由于HA微球具有比表面积大、流动性好、质量轻、强度大,注射性能好,团聚能力低等HA块材不具有的特点,其在载体、骨修复材料、环境保护和色谱分离上有广泛的应用。针对HA微球在应用过程中遇到的问题,可采用表面改性或包覆、掺杂和将HA分散在其他基体中等措施对HA微球进行功能化修饰。HA 微球在控释载体、蛋白质分离以及细胞支架等方面具有极大的应用前景。 相似文献
200.
在聚2,7-(9,9-二辛基)芴(PFO)和30%的2-(对联苯基)-5-(对叔丁基苯基)-1,3,4-噁二唑(PBD)主体材料中掺杂短磷光寿命的meso-四(对正葵酰氧基苯基)卟啉铂(TDPPPt),制成聚合物基发光器件。 器件结构为:ITO/PEDOT∶PSS/PVK/PFO+30%PBD∶TDPPPt/Ca/Al(ITO:氧化铟锡;PEDOT:聚3,4-乙撑二氧噻吩;PSS:聚苯乙烯磺酸盐;PVK:聚乙烯基咔唑)。 当客体掺杂浓度≥3%时,器件给出饱和的红色发射。 当驱动电压从7 V升高至14 V时,器件发光色度保持不变,CIE(国际发光照明委员会)色坐标稳定在(0.66,0.28)左右。 器件的最大亮度和电流效率分别为1.390 cd/m2和1.34 cd/A。 在电流密度100×10-3和150×10-3 A/cm2时,电流效率分别为1.18和0.99 cd/A,器件在高电流密度下具有良好的稳定性。 相似文献