Preparation and Characterization of Transparent Polyimide Nanocomposite Films with Potential Applications as...

Optically transparent polyimide (PI) films with good dielectric properties and long-term sustainability in atomic-oxygen (AO) environments have been highly desired as antenna substrates in low earth orbit (LEO) aerospace applications. However, PI substrates with low dielectric constant (low-D_k), low dielectric dissipation factor (low-D_f) and high AO resistance have rarely been reported due to the difficulties in achieving both high AO survivability and good dielectric parameters simultaneously. In the present work, an intrinsically low-D_k and low-D_f optically transparent PI film matrix, poly[4,4'-(hexafluoroisopropylidene)diphthalic anhydride-co-2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane] (6FPI) was combined with a nanocage trisilanolphenyl polyhedral oligomeric silsesquioxane (TSP-POSS) additive in order to afford novel organic-inorganic nanocomposite films with enhanced AO-resistant properties and reduced dielectric parameters. The derived 6FPI/POSS films exhibited the D_k and D_f values as low as 2.52 and 0.006 at the frequency of 1 MHz, respectively. Meanwhile, the composite films showed good AO resistance with the erosion yield as low as 4.0 × 10^-25 cm³/atom at the exposure flux of 4.02 × 10²⁰ atom/cm², which decreased by nearly one order of magnitude compared with the value of 3.0 × 10^-24 cm³/atom of the standard PI-ref Kapton^® film.