Hard, tough and fast self-healing thermoplastic polyurethane

It's necessary to develop self-healing polymers, which will significantly improve the safety and service life of artificial materials. Although extensive research efforts have been devoted to the field, it is still a challenge to synthesize hard and tough polymers, which own self-healing ability under mild conditions. In this work, we fabricated a hard and tough thermoplastic polyurethane (TPU, PCL-HM) and the wound of PCL-HM can be quickly healed under mild conditions (50 °C). Comprehensive characterization results suggest that the Young's modulus, tensile strength and elongation at break of PCL-HM can reach 76 MPa, 11.8 MPa and 841%, respectively, which is better than most recently reported TPUs. PCL-HM prepared with aromatic disulfide bonds as dynamic covalent bonds, polycaprolactone diol (PCL-2000) as soft segment, isophorone diisocyanate (IPDI) and dicyclohexylmethane-4,4′-diisocyanate (HMDI) as hard segment, can quickly recover to 92% of its original tensile strength within 1 h at 50 °C. Due to the better segment movement and looser packing of aromatic disulfide in PCL-HM, the PCL-HM displays better healing properties compared with other types of TPUs (PCL-I, PCL-H, PCL-M, PCL-HM′) prepared in this work. In addition, the fast healing properties of PCL-HM under mild conditions endow it with great application prospects in the field of protective coatings. The successful preparation of PCL-HM also provides a new idea for the synthesis of hard and tough TPU.