Synthesis and application of self-healing elastomers with high healing efficiency and mechical properties based on multi-healing systems

Intrinsic self-healing materials designed by combining reversible valence bonds or ionic coordination have attracted much attention due to their ability to recover from mechanical damage. However, their mechanical properties tend to deteriorate due to the increased rigidity of the chain. In this work, we report a self-healing polyurethane elastomer with multiple healing systems. 3,3′-dithiodipropionic acid (TDPA) and iron ion-2,6-diaminopyridine (DAP) were used as dynamic chain extenders and ionic ligands, respectively. They can be effectively unsealed at a certain temperature to ensure that the self-healing efficiency is not affected by the material formula. By changing the content of hard and soft segments, the mechanical properties and self-healing properties of the material can be adjusted in a large range. When the molar ratio of TDPA and DAP is 0.5:0.5, the polyurethane based on multiple healing system only needs to be healed at 70 °C for 12 h, and the self-healing efficiency can reach 93.48%. The structural rigidity and high reversibility of metal complexing agent DAP and iron ions play an important role in enhancing mechanical strength and maintaining self-healing efficiency at 70 °C. Based on the above research, we prepared the strain sensor by combining self-healing polyurethane and conductive graphene. The sensor can respond to external force quickly and stably. This work provides a feasible strategy for the preparation of mechanically robust polyurethane elastomers and self-healing flexible stress sensors with high self-healing efficiency at 70 °C.