Polydopamine nanotube for dual bio-inspired strong, tough, and flame retarding composites

To realize green, light weight, strong, tough and additional functionalities in polymer composites is challenging and has attracted great attention recently. Nature has provided perfect models such as mussel and silk to guide the design and fabrication of manmade materials with these merits. Herein, two bio-inspired strategies are combined to construct a strong, tough, and flame retarding composites. Mussel-adhesive-inspired polydopamine nanotube (PDANT) with high aspect ratio is first prepared by using a readily removable ammonium molybdate nanowire as template. PDANT/poly(vinyl alcohol) (PVA) composites with abundant and arranged interfacial hydrogen bonds (H-bonds) that mimic the hierarchically and densely assembled H-bonds in nanocrystallines reinforced spider silk are then fabricated by solution casting. Tensile test reveals that these designs have significantly improved the strength and ductility of composites as compared to neat PVA and polydopamine nanoparticles reinforced PVA. Moreover, limiting oxygen index and vertical burning test indicate that PDANT could also act as excellent flame retardant to enhance the flame resistance of composites, owing to the percolation network of PDANT in matrix and the good radical scavenging ability of PDANT. Our finding underlines the great potential of PDANT as green alternative of inorganic nanotubes for strong, tough, and flame retarding polymer composites.