The addition of hard fillers to a polymer matrix is a well-known process for achieving mechanical reinforcement. With a decrease in the size of the fillers, the contribution from polymer–particle nanometer-sized interfaces becomes significant, and these interfaces affect the mechanical performance of polymer nanocomposites (PNCs) beyond the limits established for conventional composites. However, the molecular mechanisms underlying the improvement in the mechanical performance of glassy PNCs remain unresolved, necessitating a deeper understanding of the structure–property relationships in these intrinsically heterogeneous systems. In this effort, by using Brillouin light scattering (BLS) and dynamic mechanical analysis (DMA), we demonstrated that adding shorter chains to a PNC prepared with high molecular weight polymers significantly improved the mechanical properties of the PNC in the glassy state. The strongest enhancement of mechanical properties occurred at an optimum concentration of short chains. This is in contrast to the behavior of the glass transition temperature of PNCs which shows a monotonic decrease with an increase in the concentration of shorter chains. Using experimental data and coarse-grained molecular dynamics (MD) simulations, we have identified the molecular mechanism leading to the observed nonmonotonic changes in mechanical reinforcement. This mechanism includes changes in the nanoscale organization at the interface combined with chain stretching amplified by the addition of the short chains. Overall, our approach paves a simple and cost-effective pathway to fabricating glassy PNCs with significantly improved mechanical properties that will fill various practical needs.

中文翻译：

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短聚合物链的添加会机械增强玻璃态的聚（2-乙烯基吡啶）-二氧化硅纳米颗粒纳米复合材料

向聚合物基质中添加硬质填料是实现机械增强的众所周知的方法。随着填料尺寸的减小，聚合物-颗粒纳米级界面的贡献变得显着，并且这些界面影响了聚合物纳米复合材料（PNC）的机械性能，超出了常规复合材料的极限。然而，改善玻璃状PNC力学性能的分子机制仍未解决，因此需要更深入地了解这些固有异质系统中的结构-性质关系。为此，通过使用布里渊光散射（BLS）和动态力学分析（DMA），我们证明，向由高分子量聚合物制备的PNC中添加较短的链，可显着改善玻璃态PNC的机械性能。机械性能的最强增强发生在短链的最佳浓度下。这与PNC的玻璃化转变温度的行为相反，PNC的玻璃化转变温度随着较短链的浓度的增加而单调降低。使用实验数据和粗粒度分子动力学（MD）模拟，我们确定了导致机械增强中观察到的非单调变化的分子机理。该机制包括界面处纳米级组织的变化，以及通过添加短链而放大的链拉伸。总体，