Janus polyimide films with outstanding AO resistance, good optical transparency and high mechanical strength

Highlights: • Janus polyimide films consisting of HBPSi enriched and scanty sides are fabricated. • The Janus structure is constructed by using the 'twice-cast strategy'. • Janus polyimide films show both excellent AO resistance and mechanical properties. • Janus polyimide films demonstrate high optical transparency after AO exposure. Polyimide films are required onboard spacecrafts withstanding atomic oxygen (AO) erosion in low earth orbit environment. We report a janus polyimide composite film consisting of HBPSi enriched and scanty surfaces/sides. This unique structure ensures both outstanding AO resistance—with relative mass loss merely 8.34% that of standard Kapton H—and admirable mechanical performance with ultimate tensile strength as high as ca. 89 MPa and fracture toughness up to 5.22 MJ·m⁻³. Besides, janus polyimide composite films are good at maintaining its surface morphology and integrity upon AO attack, showing a higher transmittance after AO exposure (ca. 82% at 600 nm) and lower root mean square roughness (RMS) value (5.14 nm vs. 6.62 nm) in comparison to its monolayered counterpart. These janus polyimide films demonstrate exceptional performance and thus show great potential for making surface protective blanket for spacecrafts functioning in space environment.