Porous highly fluorinated polyimide/polydopamine nanocomposite films with simultaneously enhanced toughness, UV-shielding and photostability for aerospace applications

Polydopamine (PDA), also known as artificial melanin, was adopted as ultraviolet absorbent to prepare a series of porous highly fluorinated polyimide/polydopamine (FPI/PDA) films by cyclodehydration via chemical and thermal imidization. The hydrogen bond and porous structure endowed the reinforced thermal, mechanical, UV-shielding and photostability. The initial decomposition and glass transition temperatures of FPI/PDA (1 wt %) film were as high as 461.5 °C and 341.5 °C, respectively beyond pure FPI by 54.1 °C and 26.0 °C. The stress-strain curves indicated that tensile strength and fracture elongation first increased and then decreased with the increase of PDA content, and reached the maximum at 0.5 wt % PDA content, which were 1.41 and 29.47 times of FPI, respectively. UV–vis transmittance spectra, curcumin photolysis and recyclability measurement confirmed the splendid UV-shielding properties with simultaneous excellent visible light transmittance and durability of porous FPI/PDA film. FTIR and AFM manifested its superior photostability with mild variation in carbonyl absorption peaks and surface roughness after 720 h UV irradiation. The above enhancement mechanisms included synergistic UV absorption of porous FPI and PDA, photothermal conversion in a stable FPI, and PDA's free radical trapping, promoting porous FPI/PDA film as an aerospace UV shielding material.