Tunable interfacial interaction intensity: Construction of a bio-inspired interface between polydopamine and energetic crystals

Polymer bonded explosives (PBXs) have weak strength and toughness, as well as they are prone to fracture under stress. To overcome these disadvantages, inspired by the strong adhesion of mussels and the hierarchical structure of nacre, we designed and fabricated novel PBX composites by coating three explosive crystals (2,6diamino-3,5-dinitropyrazine-1-oxide, LLM-105; 1,3,5-triamino-2,4,6-trinitrobenzene, TATB; and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, HMX) with polydopamine (PDA), respectively. The results of mechanical analysis and in situ small angle neutron scattering measurements showed that these novel PBX composites exhibited higher strength, stronger toughness, and higher creep resistance, and higher microstructural thermal stability simultaneously, compared to PBXs without multiple bio-inspired designs. Contact angles measurements indicated that the interfacial interaction intensities between energetic crystals and polymer binder could be largely enhanced by PDA coating on energetic crystals. Theoretical calculations revealed that PDA-modified PBX-LLM-105 achieved the most increment in mechanical strength, which were well consistent with the experiments. An enhancement mechanism combining the van der Waals forces, pi-pi interaction, and hydrogen bonds, as well as surface roughness was proposed to account for the variety of mechanical properties and microstructural thermal stability of PDA-modified PBXs. The results revealed in this study are commonly significant to interfacial modification and performance enhancement of materials.