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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Molecular dynamics simulations of the structural, mechanical and visco-elastic properties of polymer nanocomposites filled with grafted nanoparticles
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Molecular dynamics simulations of the structural, mechanical and visco-elastic properties of polymer nanocomposites filled with grafted nanoparticles

机译：接枝纳米粒子填充的聚合物纳米复合材料的结构，机械和粘弹性的分子动力学模拟

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摘要

Through coarse-grained molecular dynamics simulations, we have studied the effects of grafting density (S) and grafted chain length (L-g) on the structural, mechanical and visco-elastic properties of end-grafted nanoparticles (NPs) filled polymer nanocomposites (PNCs). It is found that increasing the grafting density and grafted chain length both enhance the brush/matrix interface thickness and improve the dispersion of NPs, but there seems to exist an optimum grafting density, above which the end-grafted NPs tend to aggregate. The uniaxial stress-strain behavior of PNCs is also examined, showing that the tensile stress is more enhanced by increasing Lg compared to increasing S. The tensile modulus as a function of the strain is fitted following our previous work ( Soft Matter, 2014, 10, 5099), exhibiting a gradually reduced non-linearity with the increase of S and Lg. Meanwhile, by imposing a sinusoidal external shear strain, for the first time we probe the effects of S and Lg on the visco-elastic properties such as the storage modulus G ', loss modulus G '' and loss factor tan delta of end-grafted NPs filled PNCs. It is shown that the non-linear relation of G ' and G '' as a function of shear strain amplitude decreases with the increase of S and Lg, which is consistent with experimental observations. We infer that the increased mechanical and reduced non-linear visco-elastic properties are correlated with the enhanced brush/matrix interface and therefore better dispersion of NPs and stronger physical cross-linking. This work may provide some rational means to tune the mechanical and visco-elastic properties of end-grafted NPs filled polymer nanocomposites.
机译：通过粗粒分子动力学模拟，我们研究了接枝密度（S）和接枝链长（Lg）对端接纳米颗粒（NPs）填充的聚合物纳米复合材料（PNCs）的结构，机械和粘弹性的影响。发现增加接枝密度和接枝链长度均增加了刷/基质界面的厚度并改善了NP的分散，但是似乎存在最佳的接枝密度，在此之上，末端接枝的NP趋于聚集。还检查了PNC的单轴应力-应变行为，表明与增加S相比，增加Lg可以使拉伸应力得到更大的增强。根据我们先前的工作拟合了作为应变函数的拉伸模量（Soft Matter，2014，10 （5099），随着S和Lg的增加，非线性逐渐减小。同时，通过施加正弦形的外部剪切应变，我们首次探究了S和Lg对粘弹性的影响，例如端接枝的储能模量G'，损耗模量G''和损耗因子tan delta NP填充了PNC。结果表明，随着S和Lg的增加，G'和G''的非线性关系随剪切应变幅值的变化而减小，这与实验结果一致。我们推断，增加的机械性能和降低的非线性粘弹性与增强的笔刷/矩阵界面相关，因此与NP更好的分散性和更强的物理交联性相关。这项工作可能提供一些合理的方法来调节末端接枝的NPs填充的聚合物纳米复合材料的机械和粘弹性。

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