Improvement for the mechanical performance of boroxine-based self-healing polyurethane by quadruple hydrogen bonds

The self-prepared boroxine-based polyurethane has excellent self-healing property, but its mechanical strength is poor, so a functional monomer 5-(2-hydroxyethyl)-6-methyl-2-aminouracil containing UPy motif (HMA) as non-covalent dynamic reversible bond was introduced into the polyurethane matrix to prepare HMA reinforced boroxine-based self-healing polyurethane (HmBPU). The results showed that when the dosage of HMA was 4 mmoL, the tensile strength of H4BPU film was the best which increased to 3.64 MPa from 2.05 MPa, while the self-healing efficiency increased to 70.81% from 60.06%, which indicated that the introduction of HMA had positive effect to the self-healing and mechanical strength. In addition, the recovery efficiency and mechanical strength of H4BPU still reached to 89.29% and 3.25 MPa after three cycles, which indicated that H4BPU had good recycling performance. Compared with H0BPU, the water contact angle of H4BPU increased by 16 degrees, which indicated that the water resistance of H4BPU was improved. Atomic force microscope (AFM) images showed that the degree of microphase separation of H4BPU was reduced. It is beneficial for the mixed version of double dynamic reversible covalent bonds and non-covalent bonds to improve the strength of self-healing polyurethane. Meantime, it provides a reference for the balance of the mechanical strength and self-healing performance. image