The development of degradable polymeric materials such as degradable polyurethane or polyurea has been much highlighted for resource conservation and environmental protection. Herein, a facile strategy of constructing mechanically strong and tough poly(urea-urethane) (PUU) thermosets that can be degraded under mild conditions by using triple boron-urethane bonds (TBUB) as cross-linkers is demonstrated. By tailoring the molecular weight of the soft segment of the prepolymers, the mechanical performance can be finely controlled. Based on the cross-linking of TBUB units and hydrogen-binding interactions between TBUB linkages, the as-prepared PUU thermosets have excellent mechanical strength of ≈40.2 MPa and toughness of ≈304.9 MJ m⁻³. Typically, the PBUU900 strip can lift a barbell with 60 000 times its own weight, showing excellent load-bearing capacity. Meanwhile, owing to the covalent cross-linking of TBUB units, all the PUU thermosets show initial decomposition temperatures over 290 °C, which are comparable to those of the traditional thermosets. Moreover, the TBUB cross-linked PUU thermosets can be easily degraded in a mild acid solution. The small pieces of the PBUU sample can be fully decomposed in 1 m HCl/THF solution for 3.5 h at room temperature.

中文翻译：

---

机械强度高且坚韧的聚（脲-聚氨酯）热固性材料能够在温和条件下降解

可降解聚氨酯或聚脲等可降解高分子材料的开发已成为节约资源和保护环境的重点。在此，展示了一种通过使用三硼-氨基甲酸酯键 (TBUB) 作为交联剂构建机械强度高且坚韧的聚（脲-氨基甲酸酯）（PUU）热固性材料的简便策略，该热固性材料可以在温和条件下降解。通过调整预聚物软链段的分子量，可以很好地控制机械性能。基于 TBUB 单元的交联和 TBUB 键之间的氢键相互作用，所制备的 PUU 热固性材料具有 ≈40.2 MPa 的优异机械强度和 ≈30​​4.9 MJ m −3 的^韧性. 通常情况下，PBUU900条带可以举起自身重量60000倍的杠铃，表现出出色的承重能力。同时，由于 TBUB 单元的共价交联，所有 PUU 热固性材料的初始分解温度均超过 290 °C，与传统热固性材料相当。此外，TBUB 交联 PUU 热固性塑料在弱酸溶液中很容易降解。PBUU 样品的小块可以在 1  m HCl/THF 溶液中在室温下完全分解 3.5 小时。