Lin Cuiling, Hou Fangwei, Zhang Qian, Zhu Guiqiang, Cheng Mengjiao, Shi Feng
State Key Laboratory of Chemical Resource Engineering & Beijing Laboratory of Biomedical Materials & Beijing Advanced Innovation Centre for Soft Matter Science and Engineering, Beijing University of Chemical Technology, 15 Beisanhuan East Road, Chaoyang, Beijing, 100029, China.
Small. 2024 Nov;20(48):e2404526. doi: 10.1002/smll.202404526. Epub 2024 Sep 6.
Macroscopic self-assembly of µm-to-mm components (dimension from 100 µm to millimeters), is meaningful to realize the concept of "self-assembly at all scales" and to understand interfacial phenomena such as adhesion, self-healing, and adsorption. However, self-assembly at this length scale is different from molecular self-assembly due to limited collision chances and binding capacity between components. Long-time contact between components is requisite to realize µm-to-mm assembly. Even though the recent idea of adding a compliant coating to enhance the molecular binding capacity is effective for such self-assembly, a trade-off between coating thickness (several micrometers) and assembly efficiency exists. Here a new compliant coating of surface-initiated polymer brush to address the above paradox by both realizing fast assembly and reducing the coating thickness to ≈40 nm by two magnitudes is demonstrated. Millimeter-sized quartz cubes are used as components and grafted with oppositely charged polyelectrolyte brushes, enabling assembly in water by electrostatic attraction and disassembly in NaCl solutions. A rule of thickness-dependent assembly chance is obtained and understood by in situ force measurements and a multivalent theory. The polymer brush strategy pushes the thickness limit of requisite compliant coating to the nanoscale for fast µm-to-mm self-assembly and provides insights into rapid wet adhesion.
微米到毫米级组件（尺寸从100微米到毫米）的宏观自组装，对于实现“全尺度自组装”概念以及理解诸如粘附、自修复和吸附等界面现象具有重要意义。然而，由于组件之间的碰撞机会和结合能力有限，这种长度尺度的自组装不同于分子自组装。组件之间需要长时间接触才能实现微米到毫米级的组装。尽管最近添加柔顺涂层以增强分子结合能力的想法对于这种自组装是有效的，但涂层厚度（几微米）和组装效率之间存在权衡。在此展示了一种新型的表面引发聚合物刷柔顺涂层，通过实现快速组装并将涂层厚度降低两个数量级至约40纳米，解决了上述矛盾。毫米级石英立方体用作组件，并接枝带相反电荷的聚电解质刷，使其能够在水中通过静电引力进行组装，并在氯化钠溶液中进行拆卸。通过原位力测量和多价理论获得并理解了厚度依赖的组装机会规则。聚合物刷策略将快速微米到毫米级自组装所需柔顺涂层的厚度极限推至纳米尺度，并为快速湿粘附提供了见解。
