Supramolecular structures of macromolecules containing bipyridine–copper(I) complexes as revealed from transmission electron microscopy studies

Transmission electron microscopy (TEM) studies on bipyridine (bpy) containing block copolymer systems showed the formation of nanoscopic polymer–ion complexes through complexation with copper(I) ions which segregated to highly ordered columnar domains of mesoscopic dimensions. The domains, i.e. stacks of [(bpy)₂Cu(I)] complex moieties could be visualized by complementary TEM techniques. First, electron energy loss spectra (EELS) showed the absorption edges of copper and nitrogen, which are specific for the bipyridine copper complexes. The element spectroscopic imaging (ESI) technique allowed the imaging of the net copper and net nitrogen distribution, and the coinciding pictures exhibited a microphase separated system in the case of a 3-block copolymer with complexed end segments. High resolution elastic bright field images showed interference lines with a line to line distance of about 8 A which could be related to the Cu–Cu distance in staggered Cu(I)–bipyridine complexes. Received: 6 August 1997 Accepted: 28 April 1998     

Luminescence Properties of Tb-Doped Yttrium Disilicate Prepared by the Sol–Gel Method

A sol–gel method for the synthesis of nanosized powders of yttrium disilicate doped with Tb^{3 +} is presented. The influence of grain size and annealing temperature on the structure and luminescence properties of the materials obtained has been investigated. The preparation of glass-ceramic composite has been also described. The effect of incorporating the nanocrystals into sol–gel silica glasses on their physicochemical properties has been shown and discussed. A lack of influence of the annealing above 1300°C on the lifetimes measured for the nanocrystals embedded in the glass, as compared to the Y₂Si₂O₇:Tb^{3 +} powders, has been observed.     

Mesoporous electrode material from alumina-stabilized anatase TiO2 for lithium ion batteries

A mesoporous electrode material whose structure is composed of anatase nanocrystals stabilized by alumina is reported. Powder X-ray diffraction shows the anatase phase only, but micro-Raman spectroscopy shows that the materials have a core-shell morphology with grains of bulk anatase covered by a thin rutile layer on the surface. This structure is unique when compared to analogous materials stabilized by zirconia (PNNL-1). Nitrogen adsorption isotherms demonstrate a monotonous increase in surface area and mesopore volume with increasing Al content. Thin film electrodes from these materials were characterized by lithium insertion electrochemistry. Cyclic voltammograms exhibit significant differences in Li accommodation in Al-free and Al-stabilized materials.     

Formation and Physicochemical Features of Hybrid Threadlike Micelles in Aqueous Solution

We investigate the construction of long, stable hybrid threadlike micelles consisting of polyelectrolytes and oppositely charged surfactants in aqueous solution and examine the physicochemical features such as their structure and viscoelastic behavior in aqueous solution. The most important point for their construction is the careful control of interactions, especially electrostatic interactions, caused between the surfactants and polyelectrolytes. Incorporated polyelectrolytes are fully extended in these hybrid threadlike micelles irrespective of the molecular weight of the polymer. The viscoelastic behavior of the hybrid threadlike micellar solution is similar to that of ordinary threadlike micellar systems consisting of low‐molecular‐weight substances. However, the inclusion of polymers in the micelles causes differences in their mechanical properties.     

含L－氨基酸结构的手性液晶化合物的合成及其相变行为

合成了９种具Ｌ－氨基酸衍生物结构的介晶化合物（Ｉ－Ⅲ，Ⅳａｂ，Ⅴａ，ｂ，Ⅵａ，ｂ）、４种氨基酸衍生物（Ａ１－４）和６种介晶化合物（Ｍ１－６）．新化合物（Ⅰ－Ⅲ，Ⅳａ，ｂ，Ⅴａ，ｂ，Ⅵａ，ｂ，Ａ４，Ｍ３－６）的化学结构通过ＩＲ、１ＨＮＭＲ和元素分析证实；并用偏光显微观察和ＤＳＣ分析研究了其相变行为，结果表明有８种化合物（Ｍ３－６，Ⅵａ，ｂ，Ⅴｂ，Ⅵｂ）呈现液晶相变。测定了它们的比旋光度。通过Ｘ射线衍射研究了化合物Ⅵｈ１２０～１３０℃和Ⅵｂ１７０～１８０℃的近晶结构，Ⅵｂ显，Ⅵｂ呈。测定了化合物Ⅳｂ的电滞回线，证明其具铁电性。     

La2O3,Y2O3-Mo次级发射材料研究

采用粉末冶金方法制备了La2O3，Y2O3-Mo次级发射材料，测试了各种材料的次级发射系数。结果表明在钼中加入稀土氧化物可以具有很好的次级发射性能。经过激活处理后，材料的最大次级发射系数均高于2．0，达到了材料使用要求的发射水平。应用扫描电镜(SEM)和光电能谱仪(XPS)研究了稀土元素在烧结体断口和发射前后在试样表面的分布情况。分析结果表明稀土元素易于在晶界处偏聚，且发射后试样表面稀土元素的相对浓度明显高于发射前的浓度。     

基于交叉共轭结构的功能材料

近年来,人们对交叉共轭体系的制备、性能以及理论研究方面产生了极大的兴趣。本文综述了近期国内外在交叉共轭体系研究方面取得的一些最新进展,重点介绍了其在自组装、有机电致发光和离子检测等方面的最新发展动态。最后还对本课题组在交叉型p-n双嵌段寡聚物方面的研究作了详细的介绍,并对一些热点问题作了展望。     

WHOLLY-AROMATIC THERMOTROPIC LIQUID CRYSTALLINE POLYMER AND ITS BLOCK COPOLYMER

A wholly-aromatic thermotropic liquid crystalline polymer (WATLCP) composed ofp-hydroxybenzoic acid (HBA), 4,4'-dihydroxy bisphenyl (BP), terephthalic acid (TPA),m-phthalic acid (MPA) was synthesized. It was symbolized by BP-LCP. Using a simi-lar method, a new copolymer BP-PSF was prepared. BP-PSF has a semi-flexible chainpolysulfone and a rigid-rod chain like BP-LCP. By FT-IR, polarizing microscope and DSCtechnique, the structures and properties of BP-LCP and BP-PSF were studied.     

复合生物材料的研究进展

从力学性能的改善和降解速率的可调度等角度,总结了复合生物材料与单一组分的材料相比,在生物医学领域应用中所表现出的综合使用性能的优越性。综述了复合生物材料,特别是用于骨修复的各类有机／无机复合材料近年来的研究进展状况。提出将与人骨中磷灰石微晶类似的羟基磷灰石纳米粒子与可降解聚酯材料进行复合,能够得到具有优越骨诱导性能并且能够降解的新型骨修复材料。这方面的研究代表了有机／无机复合生物材料领域新的发展方向。     

Co‐Conformational Distribution of Nanosized [2]Catenanes Determined by Pulse EPR Measurements

The co‐conformational ensembles of three differently sized [2]catenanes were studied by measuring pair correlation functions corresponding to the separation of nitroxide spin labels—one attached to each of the two macrocycles—with the double electron–electron resonance (DEER) experiment. A geometric model for the [2]catenanes was derived that approximates the macrocycles by circles and takes into account the topological constraint. Comparison of the experimental to the theoretically predicted pair correlation functions gives insight into the co‐conformational distribution and the size of the macrocycles. It was found that the macrocycles of the medium‐ and large‐sized catenanes in chloroform are close to fully expanded, while they are partially collapsed in glassy o‐terphenyl. For the small‐sized catenane, moderate interaction between the unsaturated sections of the macrocycles in chloroform is indicated by a slight overrepresentation of short label‐to‐label separations in the pair correlation function.