Superior Energy Dissipation by Ultrathin Semicrystalline Polymer Films Under Supersonic Microprojectile Impacts

Distinct deformation mechanisms that emerge in nanoscale enable the nanostructured materials to exhibit outstanding specific mechanical properties. Here, we present superior microstructure- and strain-rate-dependent specific penetration energy (up to ∼3.8 MJ kg^-1) in semicrystalline poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) thin films subjected to high-velocity (100 m s^-1 to 1 km s^-1) microprojectile (diameter: 9.2 μm) impacts. The geometric-confinement-induced nanostructural evolutions enable the sub-100 nm thick P(VDF-TrFE) films to achieve high specific penetration energy with high strain delocalization across the broad impact velocity range, superior to both bulk protective materials and previously reported nanomaterials. This high specific penetration energy arises from the substantial stretching of the two-dimensionally oriented highly mobile polymer chains that engage abundant viscoelastic and viscoplastic deformation mechanisms that are further enhanced by the intermolecular dipole-dipole interactions. These key findings provide insights for using nanostructured semicrystalline polymers in the development of lightweight, high-performance soft armors for extreme engineering applications.