Mechanically Robust and Recyclable Polyurea Networks Enabled by Dynamic Caprolactam-Urea Bonds

The integration of dynamic covalent bonds into polymer design offers transformative potential for sustainable materials.  Herein, we report a catalyst-free dynamic caprolactam-urea (CAU) bond that enables the construction of poly(caprolactam-ureas) (PCAU) networks with dual mechanical and chemical recyclability. The resulting PCAU networks exhibit remarkable mechanical robustness, solvent resistance, and hydrolytic stability. Owing to the rapid dynamic exchange of CAU bonds, PCAU networks are successfully mechanically recycled via hot-pressing over multiple cycles with >92% mechanical property retention. Furthermore, chemical recycling is achieved through selective depolymerization into caprolactam monomers under mild catalyst-free conditions, which are directly repolymerized into new generations of PCAU networks. This work establishes CAU chemistry as a versatile platform for designing high-performance dynamic polymers with applications in circular manufacturing.