Enhanced Recyclability and Durability of Solid Propellant Binders via a Dynamic Bicontinuous Structure with Self-Healing

Polyurethane with a dynamic cross-linking network provides promising next-generation solid propellant binders due to its self-healing and recyclability for improved safety and durability. However, dynamic cross-linking networks with self-healing usually lead to insufficient mechanical properties due to the contradiction between their constitutive relation and molecular chain mobility. Here, a strategy of dynamic bicontinuous structure was proposed to regulate molecular chain motion for integrated good moderate-temperature self-healing, mechanical strength, toughness, and recyclability. The acylsemicarbazide group was introduced into the polyurethane molecular chain for the formation of a stable cross-linking network and intermolecular sextuple hydrogen bonds. An asymmetric structure was designed to convert the typical island-phase morphology into a unique bicontinuous phase. The optimized chain mobility was regulated by a noncovalent reversible network of hydrogen bonds coupled with an asymmetric structure-induced bicontinuous microstructure. The obtained polyurethane exhibited an excellent mechanical strength of 51 MPa, 1410% elongation at break, a toughness of 260 MJ·m–3, and a fracture energy of 120.24 kJ·m–2. An impressive moderate-temperature self-healing of 90% was achieved within 12 h. Such a strategy provides insights for the development of high-performance binders or other high-fill energetic materials.