星型拓扑结构提高了polymer薄膜的耐冲击性
Star topology increases ballistic resistance in thin polymer films
摘要：
具有更大冲击和防弹性的聚合物膜对于许多应用是高度期望的，但是最好地满足这种需求的分子构型仍然受到争论。我们使用粗粒度的分子动力学模拟研究了聚合物薄膜的抗弹道冲击性能，研究了具有不同数目2<=f<=16和聚合度10<=M<=50的臂的线性聚合物链和星形聚合物的熔体。我们发现，增加臂的数量f或臂的长度M都导致在更大的比穿透能的参数范围内研究。在具有较大f的恒星中，更大的链相互渗透使得能量主要通过恒星内部的重排而不是链滑动来耗散。在膜变形，具有大f的恒星显示较高的能量吸收率后不久与弹丸接触，而具有较大M的恒星有一个延迟的响应，耗散主要来自链滑动，这会导致显着的背面变形。我们的研究结果表明，恒星可能是有利的调谐超薄膜的能量耗散机制。这些发现为基于拓扑结构的抗冲击聚合物薄膜设计策略奠定了基础。
英文摘要：
Polymeric films with greater impact and ballistic resistance are highly desired for numerous applications, but molecular configurations that best address this need remain subject to debate. We study the resistance to ballistic impact of thin polymer films using coarse-grained molecular dynamics simulations, investigating melts of linear polymer chains and star polymers with varying number 2<=f<=16 and degree of polymerization 10<=M<=50 of the arms. We show that increasing the number of arms f or the length of the arms M both result in greater specific penetration energy within the parameter ranges studied. Greater interpenetration of chains in stars with larger f allows energy to be dissipated predominantly through rearrangement of the stars internally, rather than chain sliding. During film deformation, stars with large f show higher energy absorption rates soon after contact with the projectile, whereas stars with larger M have a delayed response where dissipation arises primarily from chain sliding, which results in significant back face deformation. Our results suggest that stars may be advantageous for tuning energy dissipation mechanisms of ultra-thin films. These findings set the stage for a topology-based strategy for the design of impact-resistant polymer films.
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