Seeing mesoatomic distortions in soft-matter crystals of a double-gyroid block copolymer
Seeing mesoatomic distortions in soft-matter crystals of a double-gyroid block copolymer
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DOI：
10.1038/s41586-019-1706-1
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发表时间：
2019-11-07
期刊：
影响因子：
64.8
通讯作者：
Thomas, Edwin L.
中科院分区：
文献类型：
--
作者：
Feng, Xueyan;Burke, Christopher J.;Thomas, Edwin L.
超分子软晶体是由复杂成分分层组装形成的周期性结构，存在于各种“软物质”系统中(1)。由于基于通用对称性原理，此类软晶体表现出其“硬物质”原子固体对应物的许多基本特征（例如三维晶格和空间群）和属性（例如能带结构和波传播）(2,3)。软物质晶体的“介原子”构件由分子群组成，其亚晶胞结构与超单位尺度的对称性强烈耦合。迄今为止，用于表征软物质详细局部结构，特别是用于量化多尺度可重构性影响的高保真实验技术非常有限。在这里，通过应用切片和视图显微镜在大样本体积上重建溶液铸造嵌段共聚物双螺旋体的微米级域形态，我们明确地表征了其超单元和亚单元细胞形态。我们的多尺度分析揭示了这种双螺旋软晶体和硬晶体之间在响应力的结构弛豫方面的定性和未被充分认识的区别，即在大的多晶胞尺寸上一致维持的亚晶胞对称性破缺的非仿射模式。在晶体生长过程中受到不可避免的应力，双螺旋网络相对较软的支柱长度和直径可以很容易地适应变形，而角度几何形状是刚性的，即使在强烈的对称性破坏扭曲下也能保持局部相关性。这些特征与硬晶体的刚性长度和可弯曲角度形成鲜明对比。
Supramolecular soft crystals are periodic structures that are formed by the hierarchical assembly of complex constituents, and occur in a broad variety of 'soft-matter' systems(1). Such soft crystals exhibit many of the basic features (such as three-dimensional lattices and space groups) and properties (such as band structure and wave propagation) of their 'hard-matter' atomic solid counterparts, owing to the generic symmetry-based principles that underlie both(2,3). 'Mesoatomic' building blocks of soft-matter crystals consist of groups of molecules, whose sub-unit-cell configurations couple strongly to supra-unit-scale symmetry. As yet, high-fidelity experimental techniques for characterizing the detailed local structure of soft matter and, in particular, for quantifying the effects of multiscale reconfigurability are quite limited. Here, by applying slice-and-view microscopy to reconstruct the micrometre-scale domain morphology of a solution-cast block copolymer double gyroid over large specimen volumes, we unambiguously characterize its supra-unit and sub-unit cell morphology. Our multiscale analysis reveals a qualitative and underappreciated distinction between this double-gyroid soft crystal and hard crystals in terms of their structural relaxations in response to forces-namely a non-affine mode of sub-unit-cell symmetry breaking that is coherently maintained over large multicell dimensions. Subject to inevitable stresses during crystal growth, the relatively soft strut lengths and diameters of the double-gyroid network can easily accommodate deformation, while the angular geometry is stiff, maintaining local correlations even under strong symmetry-breaking distortions. These features contrast sharply with the rigid lengths and bendable angles of hard crystals.