Size-stable, smart impact-protective material fabricated via dual-network strategy with impact-hardening effect and self-healing ability

To expand their practical application scope, protective materials must be smart and stress-responsive and exhibit high energy absorption efficiency. Herein, an ideal dual-network smart protective material (denoted as PU-IHP), synthesized by the condensation polymerization of polyurethane (PU) and a novel impact-hardening polymer (IHP), was reported. The reversible softness–stiffness switchability was confirmed by the relative shear stiffening effect (RSTe), which induced the stress-responsive ability, exceeded 250. As the impact velocity increased, the impact energy absorption efficiency of PU-IHP increased, with the highest amount reaching >70%; this demonstrated that PU-IHP could efficiently reduce the impact force and extend the buffer time of strike through impact-hardening phenomenon. In addition to the excellent energy absorption efficiency, size stability and self-healing ability can be achieved through the dual-network structure of PU-IHP. These results confirmed that PU-IHP can be applied in the development of smart protective materials.