Dual-Functional Composite Coating with Flame-retardant and Antibacterial Properties for Flexible Polyurethane Foams

Abstract

Dual functionalization of polyurethane (PU) foam to achieve both flame-retardant and antibacterial properties is crucial for meeting stringent fire safety and hygiene standards. Herein, an efficient dual-functional coating, PDA@CS-POM, is developed by combining a transition metal-substituted polyoxometalate (POM), [Co4(H2O)2(PW9O34)2]10-, with a catecholamine-tethered polycation (PDA@CS(+)) using a straightforward layer-by-layer (LbL) assembly method. The catecholamine groups in PDA@CS enable effective LbL assembly on hydrophobic silicon wafers and flexible PU foams without substrate pre-treatment. In particular, the PDA@CS-POM coating achieves a growth rate of 11.3 nm/BL, more than twice that of the reference CS-POM coating. Compression-recovery cycles demonstrate that the PDA@CS-POM coating increased the toughness of the PU foam while maintaining its inherent resilience. Assessments including LOI, cone colorimetry, zone of inhibition, and colony culture tests confirm the efficient flame-retardant and antibacterial properties of the PDA@CS-POM coated PU foams. These dual-functional properties of the PDA@CS-POM coating positively correlate with the effects of the POM in inhibiting foam degradation, improving graphitization/aromatization of char barrier, and disrupting bacteria redox processes or cytoskeleton dynamics.