Bruckner Eric P, Curk Tine, Đorđević Luka, Wang Ziwei, Yang Yang, Qiu Ruomeng, Dannenhoffer Adam J, Sai Hiroaki, Kupferberg Jacob, Palmer Liam C, Luijten Erik, Stupp Samuel I
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
ACS Nano. 2022 Jun 28;16(6):8993-9003. doi: 10.1021/acsnano.2c00266. Epub 2022 May 19.
Organic crystals formed by small molecules can be highly functional but are often brittle or insoluble structures with limited possibilities for use or processing from a liquid phase. A possible solution is the nanoscale integration of polymers into organic crystals without sacrificing long-range order and therefore function. This enables the organic crystals to benefit from the advantageous mechanical and chemical properties of the polymeric component. We report here on a strategy in which small molecules cocrystallize with side chains of chemically disordered polymers to create hybrid nanostructures containing a highly ordered lattice. Synchrotron X-ray scattering, absorption spectroscopy, and coarse-grained molecular dynamics simulations reveal that the polymer backbones form an "exo-crystalline" layer of disordered chains that wrap around the nanostructures, becoming a handle for interesting properties. The morphology of this "hybrid bonding polymer" nanostructure is dictated by the competition between the polymers' entropy and the enthalpy of the lattice allowing for control over the aspect ratio of the nanocrystal by changing the degree of polymer integration. We observed that nanostructures with an exo-crystalline layer of polymer exhibit enhanced fracture strength, self-healing capacity, and dispersion in water, which benefits their use as light-harvesting assemblies in photocatalysis. Guided by computation, future work could further explore these hybrid nanostructures as components for functional materials.
由小分子形成的有机晶体可能具有高度功能性，但往往是脆性或不溶性结构，从液相进行使用或加工的可能性有限。一种可能的解决方案是将聚合物进行纳米级整合到有机晶体中，同时不牺牲长程有序性，从而不影响其功能。这使得有机晶体能够受益于聚合物组分有利的机械和化学性质。我们在此报告一种策略，即小分子与化学无序聚合物的侧链共结晶，以创建包含高度有序晶格的混合纳米结构。同步加速器X射线散射、吸收光谱和粗粒度分子动力学模拟表明，聚合物主链形成围绕纳米结构缠绕的无序链的“外结晶”层，成为有趣性质的一个抓手。这种“混合键合聚合物”纳米结构的形态由聚合物的熵与晶格焓之间的竞争决定，这使得通过改变聚合物整合程度来控制纳米晶体的纵横比成为可能。我们观察到，具有聚合物外结晶层的纳米结构表现出增强的断裂强度、自愈能力和在水中的分散性，这有利于它们用作光催化中的光捕获组件。在计算的指导下，未来的工作可以进一步探索这些混合纳米结构作为功能材料的组件。
