Robust, transparent, and self-healable polyurethane elastomer via dynamic crosslinking of phenol-carbamate bonds

Intrinsic self-healing materials designed through the incorporation of noncovalent interactions or dynamic covalent bonds are prized for their ability to recover from mechanical damages. However, they often suffer from deteriorated mechanical property due to the increased chain mobility. In this work, we reported a high-strength, colorless transparent self-healing polyurethane elastomer through dynamic crosslinking of reversible phenolcarbamate bonds. Tetrabromobisphenol A (TBBPA) and propyl gallate (PG) were used as the dynamic chain extender and dynamic crosslinking agent, respectively. They both can be effectively deblocked at mild temperatures ensuring that the self-healing efficiency is not affected by the material formulation. The mechanical properties can be tailored in a wide range by varying the crosslink density and hard segment content, and their combination uniquely determines the material formulation. The phenol-carbamate based polyurethane (PPU) with a hard segment of 60% and a crosslink density ? of 0.5 mmol cm-3 exhibited a tensile strength up to 46.4 MPa at the break strain of 615% and displayed high elastic resilience. In the meantime, it could be fully healed (?? = 93%) with 2 h of heating at 100 ?C after completely cut off. After recycled three times, it still maintained 80% of its original tensile strength. The structural rigidity of the crosslinker PG and the highly reversible phenolcarbamate bond play a crucial role in strengthening the mechanical strength while maintaining the self-healing efficiencies at elevated temperatures. This work provides a feasible strategy to prepare mechanically robust crosslinked polyurethane elastomer with high self-healing efficiency in a cost-effective manner.