Catechol-modified polymers for surface engineering of energetic crystals with reduced sensitivity and enhanced mechanical performance

Surface engineering has been widely implemented in materials science for multipurpose functionalization. However, the rational design of surface structure with both adhesiveness and toughness remains a huge challenge. Herein, a facile and general strategy has been demonstrated for coating of energetic crystal 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) via in situ copolymerization of catechol and amino functionalized monomers. The design principle is on the basis of bioinspired supramolecular chemistry, providing the synergistic effect of covalent and noncovalent interactions. Compared with the pristine HMX crystal, the coated HMX crystals exhibited significantly improved phase-transition stability and reduction of impact/friction sensitivity owing to the reinforced interfacial strength and coating roughness. Moreover, thanks to incorporation of the catechol-containing synthetic polymer (CSP) interlayer, the interfacial interaction between HMX crystal and fluoropolymer binder was noticeably enhanced, leading to markedly improved mechanical strength (both tensile and compression strength were improved by over 40%), as well as creep resistance (the creep strain was decreased by over 55%) for the resulted polymer bonded explosive (PBX) composite. Therefore, the present work provides an effective and universal method for the construction of environmental adaptive energetic materials on account of their reduced sensitivity, enhanced mechanical strength and thermal stability, which were favorable for their practical applications.