Materials by Design for Stiff and Tough Hairy Nanoparticle Assemblies
Materials by Design for Stiff and Tough Hairy Nanoparticle Assemblies
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DOI：
10.1021/acsnano.8b02454
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发表时间：
2018-08-01
期刊：
影响因子：
17.1
通讯作者：
Keten, Sinan
中科院分区：
文献类型：
--
作者：
Hansoge, Nitin K.;Huang, Tianyu;Keten, Sinan
无基质聚合物接枝纳米晶体，称为组装的毛状纳米颗粒（aHNP），可以通过克服纳米颗粒分散的挑战和通过接枝聚合物链实现更强的界面相互作用来显着提高纳米复合材料的热机械性能。然而，缺乏有效的策略来改善aHNP的机械刚度和韧性，因为这两种性质的一般冲突性质以及aHNP的设计中涉及的大量分子参数。在这里，我们提出了一个计算框架，结合多响应高斯过程元建模和粗粒度的分子动力学模拟，以建立设计策略，实现最佳的机械性能的aHNP在参数空间。以接枝到高纵横比纤维素纳米晶体上的聚（甲基丙烯酸甲酯）为模型纳米复合材料，我们的多目标设计优化框架表明，聚合物链长和接枝密度是控制aHNP力学性能的主要影响因素，相比于纳米颗粒尺寸和聚合物-纳米颗粒界面相互作用。特别是，帕累托边界，标志着设计参数空间内的机械性能的上限，可以实现当纳米粒子的重量百分比高于约60%和接枝链超过临界长度尺度控制过渡到半稀刷状政权。我们发现，理论上的缩放关系从Daoud棉花模型捕获的依赖性的临界长度尺度上的接枝密度和纳米粒子的大小。我们建立的建模框架提供了有价值的见解，这些毛茸茸的纳米粒子组件在分子水平上的机械行为，使我们能够建立纳米复合材料设计的指导方针。
Matrix-free polymer-grafted nanocrystals, called assembled hairy nanoparticles (aHNPs), can significantly enhance the thermomechanical performance of nanocomposites by overcoming nanoparticle dispersion challenges and achieving stronger interfacial interactions through grafted polymer chains. However, effective strategies to improve both the mechanical stiffness and toughness of aHNPs are lacking given the general conflicting nature of these two properties and the large number of molecular parameters involved in the design of aHNPs. Here, we propose a computational framework that combines multiresponse Gaussian process metamodeling and coarse-grained molecular dynamics simulations to establish design strategies for achieving optimal mechanical properties of aHNPs within a parametric space. Taking poly(methyl methacrylate) grafted to high-aspect-ratio cellulose nanocrystals as a model nanocomposite, our multiobjective design optimization framework reveals that the polymer chain length and grafting density are the main influencing factors governing the mechanical properties of aHNPs, in comparison to the nanoparticle size and the polymer-nanoparticle interfacial interactions. In particular, the Pareto frontier, that marks the upper bound of mechanical properties within the design parameter space, can be achieved when the weight percentage of nanoparticles is above around 60% and the grafted chains exceed the critical length scale governing transition into the semidilute brush regime. We show that theoretical scaling relationships derived from the Daoud-Cotton model capture the dependence of the critical length scale on graft density and nanoparticle size. Our established modeling framework provides valuable insights into the mechanical behavior of these hairy nanoparticle assemblies at the molecular level and allows us to establish guidelines for nanocomposite design.