<i>N</i>‑Sulfonyl Guanidine Urea\nto Design Ultrastrong, Stable, and Recyclable Associative Dynamic\nPolyurea Networks

Dynamic\ncovalent adaptive networks can solve the recycling\nissue\nof thermosets. However, dissociative dynamic covalent networks may\nsuffer from instability and network incompleteness at high temperatures\nor in solvents. Here, we report a novel dynamic covalent bond, <i>N</i>-sulfonyl guanidine urea (SGUA), that can undergo catalyst-free\nmetathesis reactions, in which a passivation strategy of increasing\nthe dissociation temperature of guanidine urea by introducing electron-withdrawing <i>N</i>-sulfonyl groups into adjacent positions was developed.\nUnlike conventional dissociative dynamic urea bonds, SGUAs exhibit\nassociative metathesis reactions at around 120–180 °C,\nwith a high dissociation threshold of 180 °C. The dynamic covalent\npolyurea constructed by SGUAs, named PSGUAs, exhibits ultrastrong\n(Young’s modulus exceeding 4 GPa and tensile strength exceeding\n60 MPa) and stable (thermal stability, network structure integrity\nunder reprocessing, and dimensional stability) performances. Furthermore,\ndue to the excellent dynamic characteristics of SGUAs, PSGUAs were\nsuccessfully reprocessed after 30–60 min of hot pressing at\n160 °C and 20 MPa. Combining the long-lasting antibacterial properties\nof PSGUAs with long-term use, this study marks a substantial improvement\nin the field of dynamic polymer networks, giving a solution for balancing\nmaterial stability, high performance, and reprocessability.