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 ($2\le f\le 16$) and degree of polymerization ($10\le M\le 50$) 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.

对于许多应用来说，具有更高冲击力和耐冲击性的聚合物薄膜是非常需要的，但是最能满足这种需求的分子构型仍需争论。我们使用粗粒分子动力学模拟研究了聚合物薄膜对弹道冲击的抵抗力，研究了线性聚合物链和数量不等的星形聚合物的熔体（$2\le F\le 16$）和聚合度（$10\le \mathrm{中号}\le 50$）的武器。我们表明，增加武器数量$F$ 或手臂的长度 $\mathrm{中号}$两者都会在所研究的参数范围内产生更大的比穿透能。更大的恒星中链的互穿程度更高$F$允许能量主要通过内部对恒星的重排而不是链滑动来耗散。薄膜变形期间，恒星较大$F$ 与弹丸接触后立即显示较高的能量吸收率，而具有较大弹丸的恒星 $\mathrm{中号}$当耗散主要来自链条滑动时，会产生延迟响应，这会导致严重的背面变形。我们的结果表明，恒星可能有利于调节超薄膜的能量耗散机制。这些发现为设计抗冲击聚合物薄膜的基于拓扑的策略奠定了基础。