Preparation of Novel Fluorinated Copolyimide/Amine-Functionalized Sepia Eumelanin Nanocomposites with Enhanced Mechanical, Thermal, and UV-Shielding Properties

Novel fluorinated copolyimide/amine-modified sepia eumelanin (ASE) nanocomposites are successfully fabricated via covalent bonds. To achieve this, the polyimide (PI) is synthesized by random co-polycondensation. The effects of ASE on the structure and properties of the PI are investigated. A multilinked network is formed with ASE acting junctions in the nanocomposites. The mechanical properties of the PI are significantly improved by the addition of ASE, and the optimal tensile strength and elongation at break are 79.7 MPa and 85.42%, respectively. UV–vis transmittance, methylene blue (MB) photodegradation, and recyclability measurements confirm that the PI/ASE nanocomposites are transparent to visible light at low ASE loadings and show outstanding UV-shielding properties and lifetimes under intense UV irradiation owing to the synergistic absorption of UV light by the PI matrix and ASE. Furthermore, the PI/ASE nanocomposites have enhanced thermal properties with initial degradation temperatures above 500 °C. These properties endow the nanocomposites with great potential for UV-shielding in the conditions with high temperature and intense ultraviolet light.