Dynamic Covalent Surface Engineering of Highly Reactive Al–Li Alloy Powders for Propellant Application

Organic functionalization of highly reactive metal powders is of great significance for chemistry and materials science yet remains a critical challenge. Herein, the interfacial self-polymerization cross-linking strategy based on boroxine chemistry is proposed to construct a functional dynamic covalent network on Al–Li alloy powders. The 4-hydroxyphenylboronic acid (HPBA) monomers undergo spontaneous dehydration and interfacial polymerization to form a trimer structure with boron–oxygen (B–O) dynamic covalent bonds in ethyl acetate solvent under vacuum and thermal conditions. During subsequent desolvation process, the HPBA trimer is further cross-linked through multimer and reactive phenolic hydroxyl groups. Dynamic B–O bonds in the boroxine structure endow the network with intrinsic self-healing capability. DFT calculation and AIMD simulation indicate that boron atoms in HPBA trimer undertake sp 3 hybridization to form robust B–O–Al/Li covalent bonds with 200.167 kJ mol –1 adsorption energy. Desolvation can generate a controllable surface morphology for the network to efficiently block corrosive media transport. This organic functionalization strategy endows Al–Li alloy-based composite solid propellants with outstanding mechanical performance (2.342 MPa tensile strength) while improving the combustion heat of Al–Li alloy fuel to 30.648 MJ kg –1 with 3.2% enhancement.