Self-assembly of carbon nanotubes in polymer melts: simulation of structural and electrical behaviour by hybrid particle-field molecular dynamics
Self-assembly of carbon nanotubes in polymer melts: simulation of structural and electrical behaviour by hybrid particle-field molecular dynamics
复制标题
聚合物熔体中碳纳米管的自组装：通过混合粒子场分子动力学模拟结构和电行为
作者：
Zhao Ying;Byshkin Maksym;Cong Yue;Kawakatsu Toshihiro;Guadagno Liberata;De Nicola Antonio;Yu Naisen;Milano Giuseppe;Dong Bin
使用混合粒子场分子动力学技术（MD-SCF）研究了分散在不同聚合物相中的碳纳米管（CNT）的自组装过程。这种高效的计算方法允许在毫秒时间尺度上模拟由珠状弹簧链制成的不同基质中柔性棒状颗粒的大规模系统（最多~1 500 000个颗粒）。较长 CNT 获得的平衡形态与几项实验研究提出的结果非常一致，这些实验研究假设 CNT 组件具有两级“多尺度”组织。此外，还使用电阻网络方法计算了组装结构的电性能。计算得出的较长碳纳米管的电导率行为与通过大量实验获得的幂律一致。特别是，根据 Bauhofer 和 Kovacs 的系统研究建立的解释，接近“统计渗滤”的系统显示出电导率对 CNT 分数的幂律依赖性的指数 t ∼ 2，而 CNT 达到平衡聚集的系统显示出指数 t 接近 1.7（“动力学渗滤”）。还使用不同的起始配置模拟了对组装结构的限制效应及其在非均质基体（例如相分离嵌段共聚物熔体）中相应的电导率行为。本文报告的模拟有助于对文献结果进行微观解释，并且所提出的建模程序可能有助于合理设计旨在优化纳米材料以改善电性能的策略。
Self-assembly processes of carbon nanotubes (CNTs) dispersed in different polymer phases have been investigated using a hybrid particle-field molecular dynamics technique (MD-SCF). This efficient computational method allowed simulations of large-scale systems (up to ∼1 500 000 particles) of flexible rod-like particles in different matrices made of bead spring chains on the millisecond time scale. The equilibrium morphologies obtained for longer CNTs are in good agreement with those proposed by several experimental studies that hypothesized a two level “multiscale” organization of CNT assemblies. In addition, the electrical properties of the assembled structures have been calculated using a resistor network approach. The calculated behaviour of the conductivities for longer CNTs is consistent with the power laws obtained by numerous experiments. In particular, according to the interpretation established by the systematic studies of Bauhofer and Kovacs, systems close to “statistical percolation” show exponents t ∼ 2 for the power law dependence of the electrical conductivity on the CNT fraction, and systems in which the CNTs reach equilibrium aggregation show exponents t close to 1.7 (“kinetic percolation”). The confinement effects on the assembled structures and their corresponding conductivity behaviour in a non-homogeneous matrix, such as the phase separating block copolymer melt, have also been simulated using different starting configurations. The simulations reported herein contribute to a microscopic interpretation of the literature results, and the proposed modelling procedure may contribute meaningfully to the rational design of strategies aimed at optimizing nanomaterials for improved electrical properties.