Self-assembly of a layered two-dimensional molecularly woven fabric
Self-assembly of a layered two-dimensional molecularly woven fabric
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DOI：
10.1038/s41586-020-3019-9
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发表时间：
2020-12-17
期刊：
影响因子：
64.8
通讯作者：
Young, Robert J.
中科院分区：
文献类型：
--
作者：
August, David P.;Dryfe, Robert A. W.;Young, Robert J.
织物（由多层编织纤维组成的材料）是日常生活中最重要的材料之一(1)。以前的纳米级编织（2-16）包括各向同性晶体共价有机框架（12-14），其特征是在所有三个维度上交织的刚性螺旋线，而不是柔性编织线的二维（17,18）层，后者赋予传统纺织品特有的柔韧性、薄度、各向异性强度和孔隙率。还报道了超分子二维 kagome 编织物 (15) 和单层、表面支撑、交织的二维聚合物 (16)。人们曾多次提出将分子构件直接自下而上组装成二维编织的线性有机聚合物链(19-23)，但此前尚未实现。在这里，我们证明，通过使用阴离子和金属离子模板，编织分子“瓦片”可以镶嵌成由交替的脂肪族和芳香族链段聚合物链组成的材料，在离散层内交织。缓慢沉淀的预编织网格之间的连接，随后去除离子模板，产生了一种完全有机的分子材料，形成薄片的堆叠和簇——每片长和宽可达数百微米，但厚度只有约四纳米——其中经向和纬向单链聚合物链通过每片内的周期性机械缠结保持关联。原子力显微镜和扫描电子显微镜显示出簇，有时还显示出孤立的单个片材，这些片材在脱金属后，已与在镶嵌和聚合过程中堆叠的其他片材分开。层状二维分子编织材料具有长程有序性，具有双折射性，其硬度是构成线性聚合物的两倍，并且以宏观纺织品的方式沿着明确的线条分层和撕裂。当合并到聚合物支撑的膜中时，它起到网的作用，减慢大离子的通过，同时让较小的离子通过。
Fabrics-materials consisting of layers of woven fibres-are some of the most important materials in everyday life(1). Previous nanoscale weaves(2-16) include isotropic crystalline covalent organic frameworks(12-14) that feature rigid helical strands interlaced in all three dimensions, rather than the two-dimensional(17,18) layers of flexible woven strands that give conventional textiles their characteristic flexibility, thinness, anisotropic strength and porosity. A supramolecular two-dimensional kagome weave(15) and a single-layer, surface-supported, interwoven two-dimensional polymer(16) have also been reported. The direct, bottom-up assembly of molecular building blocks into linear organic polymer chains woven in two dimensions has been proposed on a number of occasions(19-23), but has not previously been achieved. Here we demonstrate that by using an anion and metal ion template, woven molecular 'tiles' can be tessellated into a material consisting of alternating aliphatic and aromatic segmented polymer strands, interwoven within discrete layers. Connections between slowly precipitating pre-woven grids, followed by the removal of the ion template, result in a wholly organic molecular material that forms as stacks and clusters of thin sheets-each sheet up to hundreds of micrometres long and wide but only about four nanometres thick-in which warp and weft single-chain polymer strands remain associated through periodic mechanical entanglements within each sheet. Atomic force microscopy and scanning electron microscopy show clusters and, occasionally, isolated individual sheets that, following demetallation, have slid apart from others with which they were stacked during the tessellation and polymerization process. The layered two-dimensional molecularly woven material has long-range order, is birefringent, is twice as stiff as the constituent linear polymer, and delaminates and tears along well-defined lines in the manner of a macroscopic textile. When incorporated into a polymer-supported membrane, it acts as a net, slowing the passage of large ions while letting smaller ions through.