Wang Zaoming, Villa Santos Christian, Legrand Alexandre, Haase Frederik, Hara Yosuke, Kanamori Kazuyoshi, Aoyama Takuma, Urayama Kenji, Doherty Cara M, Smales Glen J, Pauw Brian R, Colón Yamil J, Furukawa Shuhei
Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University Yoshida, Sakyo-ku Kyoto 606-8501 Japan
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University Katsura, Nishikyo-ku Kyoto 615-8510 Japan.
Chem Sci. 2021 Aug 20;12(38):12556-12563. doi: 10.1039/d1sc02883a. eCollection 2021 Oct 6.
Assembly of permanently porous metal-organic polyhedra/cages (MOPs) with bifunctional linkers leads to soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their characterization and thus limits rational structural control. Here we demonstrate that aging is an effective strategy to control the hierarchical network of supramolecular gels, which are assembled from organic ligands as linkers and MOPs as junctions. Normally, the initial gel formation by rapid gelation leads to a kinetically trapped structure with low controllability. Through a controlled post-synthetic aging process, we show that it is possible to tune the network of the linked MOP gel over multiple length scales. This process allows control on the molecular-scale rearrangement of interlinking MOPs, mesoscale fusion of colloidal particles and macroscale densification of the whole colloidal network. In this work we elucidate the relationships between the gel properties, such as porosity and rheology, and their hierarchical structures, which suggest that porosity measurement of the dried gels can be used as a powerful tool to characterize the microscale structural transition of their corresponding gels. This aging strategy can be applied in other supramolecular polymer systems particularly containing kinetically controlled structures and shows an opportunity to engineer the structure and the permanent porosity of amorphous materials for further applications.
使用双功能连接体组装永久性多孔金属有机多面体/笼（MOPs）可形成兼具孔隙率和可加工性的软超分子网络。然而，这类软材料的无定形性质使其表征变得复杂，从而限制了合理的结构控制。在此，我们证明老化是控制超分子凝胶层次网络的有效策略，这些超分子凝胶由作为连接体的有机配体和作为节点的MOPs组装而成。通常，快速凝胶化形成的初始凝胶会导致动力学捕获结构，可控性较低。通过可控的合成后老化过程，我们表明可以在多个长度尺度上调节连接的MOP凝胶网络。此过程能够控制相互连接的MOPs的分子尺度重排、胶体颗粒的介观融合以及整个胶体网络的宏观致密化。在这项工作中，我们阐明了凝胶性质（如孔隙率和流变学）与其层次结构之间的关系，这表明干燥凝胶的孔隙率测量可作为表征其相应凝胶微观结构转变的有力工具。这种老化策略可应用于其他超分子聚合物体系，特别是含有动力学控制结构的体系，并为设计无定形材料的结构和永久孔隙率以用于进一步应用提供了机会。
