龙眼三萜-A的晶体结构

用直接法测定了龙眼三萜-A的晶体结构。晶体属单斜晶系, 空晶群C2, 晶胞参数:a=1.3419(4), b=0.6422(2), c=2.9586(7)nm, β=91.91(2)°, Vc=2.548(1)nm^3;z=4, Dc=1.12g/cm^3, Dm=1.10g/cm^3, F(000)=960。结构在MICRO VAX 计算机上用TEXSAN程序包求解、晶体结构用全矩阵最小二乘法修正, 得到最后的偏离因子R=0.068。     

Interaction of Sulfonated Calixarenes with Rhodamine B and Its Application to Determine Acetylcholine in a Real Neutral Aqueous Medium

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A versatile coating approach to fabricate superwetting membranes for separation of water-in-oil emulsions

Separation of oil/water mixtures, especially for the emulsified oil/water mixtures, is important because of the frequent occurrence of oil spill accidents. Utilizing superwetting porous membrane has become a promising approach to separate either surfactant-free or surfactant-stabilized emulsions. Herein we report a facile and versatile strategy for preparing hydrophobic/under-oil superhydrophobic membranes by coating the skeletons of the membranes with the poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) nanoparticles. The obtained membranes could be used to separate various waterin- oil emulsions with high flux and separation efficiency. In addition, owning to the outstanding resistance of PTFPMS to the most organic solvents or oils, the modified membranes exhibited the excellent reusability and the antifouling properties that were critical in the practical applications. Many commercially available membranes can be modified by such a simple method.     

聚有机硅倍半氧烷热解研究进展

国防航空工业的发展需求高性能陶瓷,尤其是纳米陶瓷。聚有机硅倍半氧烷可作为前驱体,通过热解制备陶瓷。该方法操作简便,易于控制。本文综述了国外有关聚有机硅倍半氧烷热解理论与应用研究近况,并对这一领域的发展进行了展望。     

氟化聚氨酯的合成和表征

综述了各种不同结构的氟化聚醚《型和氟化聚酯型聚氨酯的合成并对产物的化学性能进行了描述。对各种表征方法的结果讨论表明,由于结构的特殊性,氟化聚氨酯有其不同于非氟化聚氨酯的特性。     

pH敏感性两亲聚合物网络PAA—l—PTHF的研究

以具有良好柔性和生物相容性的聚四氢呋喃（ＰＴＨＦ）为疏水链段,具有ｐＨ敏感性的聚丙烯酸（ＰＡＡ）为亲水链段,通过ＰＴＨＦ双端基大分子单体与丙烯酸自由基共聚,首次合成了聚丙烯酸－ｌ－聚四氢呋喃（ＰＡＡ－ｌ－ＰＴＨＦ）两亲聚合物网络,并对网络的结构、组成以及交联点密度进行了表征。两亲聚合物网络溶胀行为研究表明,ＰＡＡ－ｌ－ＰＴＨＦ既能在水中溶胀又能在有机溶剂中溶胀,在水中的溶胀度随网络亲水链段ＰＡＡ含     

超声辐照下PEO与NaMAA嵌段共聚反应的研究

本文研究了在超声波辐照下聚氧化乙烯与甲基丙烯酸钠在水溶液中的嵌段共聚反应和共聚物结构。共聚反应按自由基聚合机理进行。反应动力学方程可用-(d[M]/(dt))=k[R·]^(1/6)[M]表示。随辐照时间或单体浓度的增加,共聚物产率和共聚物中NaMAA含量增大。将1％PEO-105％NaMAA水溶液在频率21.5kHz、阴极电流0.7A的超声强度下辐照15分钟,共聚物的产率为24.0％。用IR、MS、NMR、DSC、TEM等分析了共聚物的化学结构和聚集态结构,表明所得共聚产物为嵌段共聚物。     

Effect of water content on the size and membrane thickness of polystyrene-block-poly(ethylene oxide) vesicles

The asymmetric amphiphilic block copolymer polystyrene962-block-poly(ethylene oxide)227(PS962-b-PEO227) canforms micelles with N, N-dimethylformamide(DMF) as co-solvent and water as selected solvent, and when the water content of the mixed solvent is higher than 4.5 wt%, the vesicle will be dominated. This work finds that once vesicles are formed in the DMF-water mixed solvent, the vesicle size and membrane thickness can be tuned by further increasing water content. As the water fraction elevated from 4.8 wt% to 13.0 wt%, the vesicle size dercreases from 246 nm to 150 nm, while the membrane thickness increases from 28 nm to 42 nm. In addition, the block copolymer packing and the free energy are analyzed as the vesicle size becomes small and the membrane becomes thick.     

Effects of ultra-high temperature treatment on the microstructure of carbon fibers

The microcrystalline structure and microvoid structure in carbon fibers during graphitization process(2300-2700 °C) were characterized employing laser micro-Raman scattering(Raman), X-ray diffraction(XRD), small angle X-ray scattering(SAXS), and high-resolution transmission electron microscopy(HR-TEM). The crystalline sizes(L_a, L_c) increased and interlayer spacing(d_(002)) decreased with increasing heat treatment temperature(HTT). The microvoids in the fibers grew up and contacted to the neighbors with the development of microcrystalline. In addition, the preferred orientation of graphite crystallite along fiber axis decreased and microvoids increased. The results are crucial for analyzing the evolution of microstructure of carbon fibers in the process of heat treatment and important for the preparation of high strength and high modulus carbon fibers.