Carbon quantum dots enhanced polyurethane-urea nanocomposites with mechanical reinforcement and room-temperature self-healing performance

Developing high-performance polymer composites with self-healing and recyclable performance is crucial for long-term durability of the devices. This paper presents a novel method by incorporating carbon quantum dots (CQDs) into the chain extension reaction of polymers to construct self-healing polyurethane-urea (PUU) with excellent integrated mechanical and multi-recyclable properties. By the introduction of the CQDs with surface containing ample amide, carboxyl, and hydroxyl groups, the cross-linking networks are formed, and simultaneously, abundant H-bonds at the interface between CQDs nanospheres and PUU matrix provide strong interfacial interactions, which endows material reinforcement and self-healing effect. The addition of a very low amount of CQDs (0.15 wt%) can significantly improves the mechanical performance, especially the tensile stress and toughness, which increased about 74.4 % (35.2 MPa to 61.4 MPa) and 115.2 % (34.8 MJ.m(-3) to 74.9 MJ.m(-3)), respectively. Besides, unlike other nanofillers, the addition of CQDs (more than 1 wt%) enables the PUU with excellent self-healing and recycling properties, and for 3 wt% addition, the room temperature selfhealing efficiency can even achieve 97.0 % for 24 h without external intervention. Furthermore, the addition of the CQDs can also significantly the damping effect of the polymers. It is highly anticipated that the research will provide a facile method to construct high performance polymer materials.