Mussel-inspired copper-catechol coordination network enabled fire-retardant polylactide composites with excellent electromagnetic shielding and antibacterial properties

The development of advanced polylactide (PLA) composites that integrated intrinsic flame retardancy, electromagnetic interference (EMI) shielding, and antibacterial functionality within a single material system remained a significant challenge. Inspired by the robust metal‒phenolic coordination chemistry of mussel byssus threads, this study designs a bio-inspired copper‒catechol Schiff-base complex ( Cu@CSP ) and synergistically combined it with expandable graphite (EG) to fabricate multifunctional PLA composites. The resulting PLA- Cu@CSP +EG composite achieved a UL-94 V-0 rating with a high limiting oxygen index (LOI) of 31.6%, while completely suppressing melt dripping. Cone calorimetry revealed a 69.6% reduction in peak heat release rate (pHRR), a 40.3% decrease in total heat release (THR), and a 76.6% suppression in CO 2 production. These exceptional fire-safety metrics were attributed to a condensed-phase synergistic mechanism in which Cu@CSP catalytically promoted char formation and graphitization, while EG acted as an expanding scaffold, leading to the formation of a voluminous, thermally insulating intumescent char. Remarkably, the blends also exhibited efficient EMI shielding (>20 dB) through a reflection-absorption dual mechanism and potent broad-spectrum antibacterial activity (>99% inhibition against both S. aureus and Escherichia coli ), arising from the combined action of chitosan, copper ions, and Schiff-base structures. This work presented a rational biomimetic strategy for creating multifunctional sustainable polymers with integrated fire safety, electromagnetic compatibility, and antimicrobial properties for next-generation electronics, transportation, and healthcare applications.