Institute of Physics, University of Amsterdam, Science Park 904, Amsterdam, 1098 XH, The Netherlands.
Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Amsterdam, 1098 XH, The Netherlands.
Adv Mater. 2017 Sep;29(34). doi: 10.1002/adma.201700819. Epub 2017 Jul 10.
Recent breakthroughs in colloidal synthesis promise the bottom-up assembly of superstructures on nano- and micrometer length scales, offering molecular analogues on the colloidal scale. However, a structural control similar to that in supramolecular chemistry remains very challenging. Here, colloidal superstructures are built and controlled using critical Casimir forces on patchy colloidal particles. These solvent-mediated forces offer direct analogues of molecular bonds, allowing patch-to-patch binding with exquisite temperature control of bond strength and stiffness. Particles with two patches are shown to form linear chains undergoing morphological changes with temperature, resembling a polymer collapse under poor-solvent conditions. This reversible temperature switching carries over to particles with higher valency, exhibiting a variety of patch-to-patch bonded structures. Using Monte Carlo simulations, it is shown that the collapse results from the growing interaction range favoring close-packed configurations. These results offer new opportunities for the active control of complex structures at the nano and micrometer scale, paving the way to novel temperature-switchable materials.
最近胶体合成方面的突破有望实现纳米和微米长度尺度上的超结构的自下而上组装，为胶体尺度提供分子类似物。然而，类似于超分子化学中的结构控制仍然极具挑战性。在这里，使用带有斑点的胶体粒子上的临界 Casimir 力来构建和控制胶体超结构。这些溶剂介导的力提供了分子键的直接类似物，允许斑点到斑点的结合，并具有对键强度和刚性的精细温度控制。具有两个斑点的粒子被证明可以形成线性链，随着温度的变化而发生形态变化，类似于在不良溶剂条件下的聚合物坍塌。这种可逆的温度切换可以扩展到具有更高配位数的粒子，表现出各种斑点到斑点键合的结构。通过蒙特卡罗模拟，表明坍塌是由于相互作用范围的增加有利于紧密堆积的构型。这些结果为在纳米和微米尺度上对复杂结构进行主动控制提供了新的机会，为开发新型温度可切换材料铺平了道路。
