Synthesis and characterization of linear self-healing polyurethane based on thermally reversible Diels–Alder reaction

New linear polyurethane was synthesized via a Diels–Alder (DA) reaction between a polyurethane prepolymer end-capped with furan groups (MPF) and bismaleimide (BMI). The structure of the linear polyurethane with DA bonds was characterized by 1H NMR, ATI-FTIR, TGA and AFM. The introduction of DA bonds enables the polyurethane thermal reversibility, which was studied thoroughly by 1H NMR, DSC and GPC. Besides, the new linear polyurethane with DA bonds also exhibits self-healing properties under heat treatment, which was observed by polarized optical microscope. The self-healing efficiency determined by the recovery of breaking tensile strength after being damaged and healed can reach up to 80%.