Self-Healing Polyurethane-Urea Elastomers with High Strength and Toughness Based on Dynamic Hindered Urea Bonds and Hydrogen Bonds

Developing polymers with high self-healing rates as well as robust mechanical properties remains a significant challenge. Herein, a series of novel self-healing polyurethane-urea (PUU) elastomers with high strength and toughness were prepared using 4,4 '-diaminodicyclohexyl methane (HMDA) and N,N '-ditert-butylethylenediamine (DBDA). The HMDA amino groups react with the alicyclic isocyanates to form strong hard segments composed of multiple alicyclic structures and strong urea hydrogen bonds. The strong hard segments play a crucial role in generating strain-induced crystallization (SIC), resulting in improved mechanical properties. The weak hard segments contain dynamic hindered urea bonds and weak hydrogen bonds, which ensures the dynamics of the system and provides the possibility for self-healing. The optimized sample (PUU-2) not only exhibits outstanding tensile strength (49.6 MPa), toughness (385.6 MJ/m3), etc. but also has a healing efficiency of up to 90.5% (at 120 degrees C for 6 h). This study presents a facile strategy for the design and fabrication of self-healable polyurethane-urea elastomers with high performance.