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.

在过去的几年中，使用树木和树突聚合物等组成块生产了复杂的有机纳米结构。这些树状分子自我组装普遍成圆柱或球（胶束），然后在各种2-D或3-D周期晶格上包装。在许多自组装的树突聚合物中观察到胶束。该相是液晶和准晶体（液体准晶体或LQC），具有独特但晶体学上的12倍对称性。这是在金属合金以外的系统中发现的第一个准晶结构。与常规晶体不同，准晶体具有远距离翻译顺序而不是周期性的，并引起了在常规晶体学中允许的2-，3-，4-和6倍以外的旋转对称性。与金属准晶体相比，LQC中的特征长度增加了近两个数量级，从几个埃埃斯特罗姆斯到近100 + +。已经确定，可以利用准晶体的异常对称性来诱导和扩大完整的光子带隙。 LQC的发现指向将结构进一步扩展到自组装的光子准晶体。在拟议的项目中，将使用透射电子显微镜来确定LQC的结构。 LQC中胶束的直径约为40 +，这一事实使得可以直接检查电子显微镜下的胶束的堆积。对于金属合金，通过衍射或显微镜测定了准晶体中原子位置的测定极为困难。使用衍射，问题本质上在准晶体对称性中：不同的原子包装可以产生相似的衍射模式。显微镜方法的问题是它们的分辨率有限：当前的实验方法无法在原子量表下可靠地解析结构。因此，LQC提供了一个独特的机会，可以明确地确定胶束在准晶体结构中的位置。将研究其他相关的复杂自我组装的纳米结构，包括其他液晶系统中可能的准晶体序三块两亲物等中的晶体，蜂窝柱结构。计算机建模将用于进一步了解自组装方式与分子结构之间的关系。将与合成化学家合作设计，能够形成以前未观察到的结构的新分子体系结构。还将努力在仍然更大的尺度上构建纳米结构，并通过自组装来构建光子带隙材料。分子筛，有机磁铁和药物释放剂。由于类似的原理指导结构形成在热型树状聚合物，裂解L.C.S和块共聚物中，因此新结构可能会导致在这些后一种系统中发现它们的等效物，从而增加了量表和应用的范围。阐明液体准晶体的结构可能会导致人们对准晶体的一般理解。该项目所涉及的技术的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