Engineering of Hierarchical Phase-Separated Nanodomains toward Elastic and Recyclable Shock-Absorbing Fibers with Exceptional Damage Tolerance and Damping Capacity

Shock-absorbing fibers (SAFs) are highly regarded for their effectiveness in energy-absorbing applications. Existing SAFs are plastic fibers that can only be used once, are nonrecyclable, and lack damage tolerance. Herein, we fabricate recyclable, mechanically robust elastic SAFs with exceptional damage tolerance via wet spinning of multiblock polyurethane (PU) composed of polycaprolactone (PCL) and polytetrahydrofuran (PTMG) segments. The SAFs are denoted as PU–PCL₇₀, achieving an ultrahigh true strength of 908.8 MPa, a high damping efficiency of 87%, and a record fracture energy of 4042 kJ m^–2. Mechanistic analysis reveals that the superior performance of PU–PCL₇₀ originated from the oriented hierarchical phase-separated nanodomains formed by hydrogen and coordination bonds and rigid PCL segments. These rigid nanodomains are capable of deformation and disintegration to effectively absorb energy. These nanodomains can autonomously re-form, enabling the fibers with reusability without treatment. The dynamic nature of these nanodomains allows for complete recyclability of PU–PCL₇₀ through respinning.