Institute of Particle Technology, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany.
G. W. Gray Centre for Advanced Materials, Department of Physics and Mathematics, University of Hull, Hull HU6 7RX, United Kingdom.
Proc Natl Acad Sci U S A. 2021 Dec 28;118(52). doi: 10.1073/pnas.2113394118.
The two-dimensional self-assembly of colloidal particles serves as a model system for fundamental studies of structure formation and as a powerful tool to fabricate functional materials and surfaces. However, the prevalence of hexagonal symmetries in such self-assembling systems limits its structural versatility. More than two decades ago, Jagla demonstrated that core-shell particles with two interaction length scales can form complex, nonhexagonal minimum energy configurations. Based on such Jagla potentials, a wide variety of phases including cluster lattices, chains, and quasicrystals have been theoretically discovered. Despite the elegance of this approach, its experimental realization has remained largely elusive. Here, we capitalize on the distinct interfacial morphology of soft particles to design two-dimensional assemblies with structural complexity. We find that core-shell particles consisting of a silica core surface functionalized with a noncrosslinked polymer shell efficiently spread at a liquid interface to form a two-dimensional polymer corona surrounding the core. We controllably grow such shells by iniferter-type controlled radical polymerization. Upon interfacial compression, the resulting core-shell particles arrange in well-defined dimer, trimer, and tetramer lattices before transitioning into complex chain and cluster phases. The experimental phase behavior is accurately reproduced by Monte Carlo simulations and minimum energy calculations, suggesting that the interfacial assembly interacts via a pairwise-additive Jagla-type potential. By comparing theory, simulation, and experiment, we narrow the Jagla g-parameter of the system to between 0.9 and 2. The possibility to control the interaction potential via the interfacial morphology provides a framework to realize structural features with unprecedented complexity from a simple, one-component system.
胶体粒子的二维自组装是研究结构形成的基本模型体系，也是制备功能材料和表面的有力工具。然而，这种自组装体系中六方对称性的普遍存在限制了其结构的多功能性。二十多年前，Jagla 证明了具有两个相互作用长度尺度的核壳粒子可以形成复杂的、非六方的最低能量构型。基于这种 Jagla 势，已经从理论上发现了包括团簇晶格、链和准晶体在内的多种相。尽管这种方法很优雅，但它的实验实现仍然难以捉摸。在这里，我们利用软粒子的独特界面形态来设计具有复杂结构的二维组装体。我们发现，由二氧化硅核表面功能化的非交联聚合物壳组成的核壳粒子在液体界面上有效地扩散，形成一个二维聚合物冠层，包围着核。我们通过引发剂型可控自由基聚合来可控地生长这种壳。在界面压缩时，所得的核壳粒子在过渡到复杂的链和团簇相之前，按规则的二聚体、三聚体和四聚体晶格排列。实验相行为可以通过蒙特卡罗模拟和最低能量计算准确再现，这表明界面组装通过一种可加的 Jagla 型相互作用势相互作用。通过比较理论、模拟和实验，我们将系统的 Jagla g 参数缩小到 0.9 到 2 之间。通过界面形态控制相互作用势的可能性为从简单的单组分体系实现具有前所未有的复杂性的结构特征提供了一个框架。
