Bioinspired mineral–organic strategy for fabricating a high-strength, antibacterial, flame-retardant soy protein bioplastic via internal boron–nitrogen coordination

Abstract Plant-derived renewable and biodegradable bioplastics are attractive alternatives to petroleum-based materials, but their applicability is limited by insufficient interface bonding and the antibacterial properties of biopolymer. Inspired by the unique hierarchical structure of nacre, we report a facile and sustainable mineral–organic strategy that fabricates a soy protein (SP)-based film with excellent mechanical strength and toughness. The nitrogen-coordinating boronic diester (NB) is synthesized from boronic acid and diols, which form enhanced cross-linking networks through dynamic glue linkages. As a glue molecule, caffeic acid (CA) containing phenolic compounds can co-assemble with hydroxyapatite (HA) in the SP matrix to produce inorganic–organic CA-functionalized HA (CHA) hybrids. The strong affinity between the NB and CHA hybrids combined with dynamic covalent bonds and sacrificial hydrogen bonds substantially improves the bonding strength and cohesion of the SP-based composites. The tensile strength and toughness of the resultant film were 13.89 MPa and 14.72 MJ/m3, respectively, 361% and 489% higher than the pristine SP film. Owing to the biomineralization and phenolic components, the incorporated NB@CHA hybrids endow the film with desirable water resistance, flame retardancy, UV protection performance, and antibacterial activity. This biomimetic strategy provides a novel and versatile fabrication route to high-performance SP-based bioplastics for engineering and biological applications.