Nomadic Molecular Key‐Driven Instantaneous Covalent Reconstruction Enables Ultrahigh Impact‐Stiffening Polymeric Armor

), yielding 97% impact-force reduction. PSTx is processable into various wearable composites with outstanding impact force attenuation (+957%) and puncture resistance (+360%). This work resolves challenges of activation thresholds and stiffening hysteresis in impact-stiffening materials, providing a molecular key-switchable paradigm for intelligent systems.