Allomelanin-Inspired Polyurethane Nanocomposites with Multi-Radiation Resistance and Enhanced Mechanical Properties

Approaches for protecting polymeric materials against ionizing radiation are of importance for applications including in space, in aseptic medical devices, and in the nuclear industry. Allomelanin is a specific subclass of nitrogen-free melanin found to play a key role in the protection of fungal species in extreme environments. Herein, we prepared allomelanin-inspired nanomaterials by oxidatively polymerizing dihydroxynapthalene (DHN) isomers 1,7-DHN and 2,3-DHN. We demonstrate that these materials can be easily dispersed into a polyurethane (PU) elastomer, yielding products with tunable mechanical properties and optical transparency. We show that at loadings as low as 0.25 wt %, this approach provides UVB protection to the PU matrix maintaining mechanical properties despite exposure, preservation of composite surface chemistry, and suppression of crack formation. Furthermore, we show that these composites maintain their mechanical properties after exposure to gamma irradiation, demonstrating the multiradiation protective effect of these allomelanin-inspired nanomaterials.