Orientational phase behavior of polymer-grafted nanocubes
Orientational phase behavior of polymer-grafted nanocubes
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DOI：
10.1039/c9nr04859f
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发表时间：
2019-09-14
期刊：
影响因子：
6.7
通讯作者：
Arya, Gaurav
中科院分区：
文献类型：
--
作者：
Lee, Brian Hyun-jong;Arya, Gaurav
最近表明，具有聚合物接枝的纳米粒子的表面功能化是控制成形纳米粒子在其高阶组件中的相对方向的可行策略。在这项研究中，我们通过计算机研究了限制在薄膜中的共面聚合物接枝纳米立方体的取向相行为。我们首先使用蒙特卡罗模拟来计算纳米立方体的两粒子相互作用自由能景观并确定其全局稳定配置。发现纳米立方体表现出四个稳定相：那些具有边缘-边缘和面-面方向的稳定相，以及那些表现出部分重叠的倾斜面和平行面的稳定相，这些面先前被认为是亚稳定的。此外，最初被认为涉及接吻边缘的边缘-边缘配置反而显示出部分重叠的边缘，其中重叠的程度取决于移植物的附着位置。接下来，我们制定了所识别构型的自由能的解析标度表达式，该表达式用于在多维参数空间中构建纳米立方体取向的综合相图，其中包括纳米立方体的尺寸和相互作用强度以及接枝物的库恩长度和表面密度。相图的形态被证明是由聚合物和表面介导的相互作用之间的相互作用产生的，特别是它们在纳米立方体尺寸和四个相的接枝密度方面的比例差异。该相图提供了通过系统的各种参数调整这些相互作用以实现目标配置的见解。总体而言，这项工作提供了一个用于预测和工程颗粒间配置的框架，并可能在等离子体纳米复合材料中应用，其中对颗粒方向的控制至关重要。
Surface functionalization of nanoparticles with polymer grafts was recently shown to be a viable strategy for controlling the relative orientation of shaped nanoparticles in their higher-order assemblies. In this study, we investigated in silico the orientational phase behavior of coplanar polymer-grafted nanocubes confined in a thin film. We first used Monte Carlo simulations to compute the two-particle interaction free-energy landscape of the nanocubes and identify their globally stable configurations. The nanocubes were found to exhibit four stable phases: those with edge-edge and face-face orientations, and those exhibiting partially overlapped slanted and parallel faces previously assumed to be metastable. Moreover, the edge-edge configuration originally thought to involve kissing edges instead displayed partly overlapping edges, where the extent of the overlap depends on the attachment positions of the grafts. We next formulated analytical scaling expressions for the free energies of the identified configurations, which were used for constructing a comprehensive phase diagram of nanocube orientation in a multidimensional parameter space comprising of the size and interaction strength of the nanocubes and the Kuhn length and surface density of the grafts. The morphology of the phase diagram was shown to arise from an interplay between polymer- and surface-mediated interactions, especially differences in their scalings with respect to nanocube size and grafting density across the four phases. The phase diagram provided insights into tuning these interactions through the various parameters of the system for achieving target configurations. Overall, this work provides a framework for predicting and engineering interparticle configurations, with possible applications in plasmonic nanocomposites where control over particle orientation is critical.