Novel complex nanostructures in supramolecular systems

超分子系统中的新型复杂纳米结构

• 批准号: EP/D068592/1
• 负责人: Xiangbing Zeng
• 金额: $ 25.12万
• 依托单位: University of Sheffield
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD068592%2F1
• 关键词: Novel; complex; nanostructures; supramolecular; systems

Over the last several years complex organic nanostructures have been produced synthetically, using building blocks such as dendrons and dendrimers. These tree-like molecules self-assemble prevalently into cylinders or spheres (micelles), which in turn pack on a variety of 2-d or 3-d periodic lattices.Recently a novel, and so far the most complex, mode of packing of micelles was observed in a number of self-assembled dendrimers. The phase is a liquid crystal as well as a quasicrystal (liquid quasicrystal or LQC), possessing the distinctive but crystallographically forbidden 12-fold symmetry. This is the first quasicrystalline structure found in systems other than metal alloys. Unlike conventional crystals, quasicrystals possess long range translational order without being periodic, and give rise to rotational symmetries other than 2-, 3-, 4-, and 6-fold, allowed in conventional crystallography. Compared to metallic quasicrystals, the characteristic length in LQC is increased by nearly two orders of magnitude, from a few angstroms to nearly 100 +. It has been established that the unusual symmetry of quasicrystals can be utilized to induce and widen the complete photonic bandgap. The discovery of LQC points the way to scaling up the structure still further toward self-assembled photonic quasicrystals.In the proposed project, transmission electron microscopy will be used to determine the structure of LQC. The fact that the diameter of the micelles in the LQC is ~40 + makes it possible to directly examine the packing of micelles under the electron microscope. Determination of atomic positions in a quasicrystal is extremely difficult for metal alloys, either by diffraction or by microscopy. With diffraction the problem lies intrinsically in the quasicrystalline symmetry: different packings of atoms can generate similar diffraction patterns. The problem with microscopy methods is their limited resolution: current experimental methods cannot reliably resolve structures at atomic scale. LQC thus provides a unique opportunity to determine unambiguously the positions of micelles in a quasicrystalline structure.Other related complex self-assembled nanostructures will be investigated, including possible quasicrystalline order in other liquid crystal systems, as well as the newly discovered triple network tricontinuous cubic liquid crystal, honeycomb columnar structures in tri-block amphiphiles, etc. Computer modelling will be used to further our understanding of the relationship between the mode of self-assembly and molecular structure. New molecular architectures, capable of forming previously unobserved structures, will be designed in collaboration with synthetic chemists. Efforts will also be made to construct nanostructures on still larger scales, with a view of constructing photonic band gap materials through self-assembly.Many of the above organic nanostructures present opportunities for engineering devices such as molecular ion-channel, molecular wires, membranes, molecular sieves, organic magnets and drug-release agents. Since similar principles guide structure formation in thermotropic dendrimers, lyotropic l.c.s and block copolymers, the new structures are likely to lead to the discovery of their equivalents in these latter systems, increasing the range of scales and applications. The elucidation of the structure of liquid quasicrystals is likely to lead to an improved understanding of quasicrystals in general. The developments in techniques involved in this project would also benefit researchers in the wider area of nanoscience.

在过去的几年里，复杂的有机纳米结构已经合成，使用构建块，如树枝状分子和树枝状聚合物。这些树枝状分子自组装成圆柱体或球体（胶束），然后填充在各种二维或三维周期晶格上。最近，在许多自组装树枝状分子中观察到了一种新颖的，也是迄今为止最复杂的胶束填充模式。相是液晶以及准晶体（液体准晶体或LQC），具有独特的，但晶体学禁止的12重对称性。这是第一个在金属合金以外的系统中发现的准晶结构。与常规晶体不同，准晶具有长程平移有序而不是周期性的，并且产生常规晶体学中允许的2倍、3倍、4倍和6倍以外的旋转对称性。与金属准晶相比，LQC中的特征长度增加了近两个数量级，从几埃增加到近100 +。人们已经确定，准晶的不寻常的对称性可以用来诱导和加宽完整的光子带隙。LQC的发现指出了将结构进一步放大到自组装光子准晶体的方法。在拟议的项目中，透射电子显微镜将用于确定LQC的结构。LQC中胶束的直径为~40 +的事实使得可以在电子显微镜下直接检查胶束的堆积。对于金属合金来说，无论是用衍射法还是显微镜法，都很难确定准晶中原子的位置。衍射的问题本质上在于准晶的对称性：原子的不同堆积可以产生相似的衍射图案。显微镜方法的问题在于其有限的分辨率：目前的实验方法无法可靠地解析原子尺度的结构。其他相关的复杂自组装纳米结构将被研究，包括其他液晶系统中可能的准晶有序，以及新发现的三重网络三连续立方液晶，三嵌段两亲分子中的蜂窝柱状结构，计算机模拟将被用来进一步了解自组装模式和分子结构之间的关系。新的分子结构，能够形成以前未观察到的结构，将与合成化学家合作设计。这些有机纳米结构为分子离子通道、分子导线、分子膜、分子筛、有机磁体和药物释放剂等工程器件提供了机会。由于类似的原则指导热致性树枝状聚合物，溶致液晶和嵌段共聚物的结构形成，新的结构很可能导致在这些后者系统中发现它们的等价物，增加规模和应用范围。液体准晶结构的阐明可能会导致一般准晶的理解得到改善。该项目所涉及的技术发展也将使纳米科学更广泛领域的研究人员受益。

项目成果

X-Shaped polyphilics: liquid crystal honeycombs with single-molecule walls.

• DOI: 10.1039/b804945a
• 发表时间: 2008-08
• 期刊: Chemical communications
• 影响因子: 4.9
• 作者: R. Kieffer;M. Prehm;Benjamin Glettner;K. Pelz;U. Baumeister;Feng Liu;X. Zeng;G. Ungar;C. Tschie