Viscoelastic and dynamic properties of polymer grafted nanocomposites with high glass transition temperature graft chains
Viscoelastic and dynamic properties of polymer grafted nanocomposites with high glass transition temperature graft chains
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DOI：
10.1063/1.5119694
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发表时间：
2019-11
影响因子：
3.2
通讯作者：
W. Peng;R. Ranganathan;P. Keblinski;Pinar Akcora;R. Ozisik
中科院分区：
文献类型：
--
作者：
W. Peng;R. Ranganathan;P. Keblinski;Pinar Akcora;R. Ozisik
采用分子动力学模拟方法研究了动态不对称聚合物接枝纳米复合材料的粘弹性和动态力学性能。模型PGN是由两个链具有大的玻璃化转变温度（Tg）的差异，其中接枝链具有较高的Tg。的粘弹性和动态性能进行了研究，在温度之间的接枝和基体聚合物的Tg的平均刷高度的函数。模拟结果表明，静态和动态性能的玻璃刷增强整体纳米复合材料中发挥了重要作用。虽然裸露的纳米填料含有纳米复合材料显示出增加的剪切储能模量相比，纯的低Tg聚合物，PGNs提出了最大的增加的剪切储能模量。此外，剪切储能模量随着平均刷高度的增加而增加，在刷高度极限处达到最大值。对模拟结果的分析表明，剪切储能模量的增强主要与基体聚合物链的动力学减慢有关。确定了以下机制是造成这种效应的原因：（i）高Tg接枝链充当基质聚合物链的障碍。(ii)随着平均刷高度的增加，接枝和基质链在纳米填料界面处形成良好混合的形态，这导致基质链动力学的进一步减慢。(iii)最后，在刷的高度限制，接枝链形成一个刚性和不动的交联网络，这导致观察到的最大剪切储能模量。
The viscoelastic and dynamic properties of dynamically asymmetric polymer-grafted nanocomposites (PGNs) are studied via molecular dynamics simulations. The model PGN is made up of two chains having a large glass transition temperature ( T g ) difference, where the grafted chains have the higher T g. The viscoelastic and dynamic properties were studied at temperatures between the T g s of the graft and matrix polymers as a function of the average brush height. Simulation results showed that the static and dynamic properties of the glassy brush played an important role in reinforcing the overall nanocomposite. Although the bare nanofiller containing nanocomposite showed increased shear storage moduli compared to the neat low- T g polymer, PGNs presented the greatest increases in the shear storage modulus. In addition, the shear storage modulus increased with increasing average brush height, reaching a maximum value at the brush height limit. Analysis of the simulation results revealed that the reinforcement of the shear storage modulus was mainly related to the slowing down of the dynamics of matrix polymer chains. The following mechanisms were identified that were responsible for this effect: (i) High- T g grafted chains act as obstacles for matrix polymer chains. (ii) With increasing average brush height, grafted and matrix chains form a well-mixed morphology at the nanofiller interface, which leads to further slowing down of the matrix chain dynamics. (iii) Finally, at the brush height limit, grafted chains form a stiff and immobile percolated network, which leads to the observed maximum in the shear storage modulus.