Abstract
<title>Abstract</title> <p> Colorless polyimide (CPI) is a highly promising flexible substrate for aerospace applications, yet it suffers from severe atomic oxygen (AO) erosion and degradation in low Earth orbit (LEO) environments. While depositing ZnO coatings offers effective protection, weak van der Waals bonding at the organic/inorganic interface makes the protective layer highly susceptible to delamination under alternating spatial stresses. To overcome this interfacial bottleneck, this study employed 3-aminopropyltriethoxysilane (APTES) to modify the CPI surface, successfully bridging the CPI/ZnO interface and revealing the microscopic enhancement mechanisms through a closed loop of multi-scale theoretical calculations and ground verifications. Rigid scan calculations demonstrate that the APTES molecular bridge significantly shortens the interfacial equilibrium distance from 2.90 Å to 2.25 Å, increasing the absolute minimum interaction energy by 2.13 times (from − 19.58 kcal/mol to -41.78 kcal/mol). Microscopic electronic structure analyses—including charge density difference, electron localization function (ELF), and partial density of states (PDOS)—reveal that APTES exerts a multi-site bidirectional anchoring effect: the amino end forms high-strength N-Zn polar coordinate bonds via deep orbital hybridization, while the siloxane group constructs a robust Si-O-Zn covalent network. These spatial charge rearrangements are perfectly corroborated by macroscopic X-ray photoelectron spectroscopy (XPS) experiments, evidenced by a positive binding energy shift of the N <italic>1s</italic> peak (399.7 eV to 404.5 eV) due to electron loss, and a negative shift of the Si <italic>2p</italic> peak (101.7 eV to 101.4 eV) driven by metal-induced electron donation. Furthermore, ab initio molecular dynamics (AIMD) and reactive molecular dynamics (ReaxFF-MD) simulations confirm that this robust hybrid interface effectively dissipates impact kinetic energy during continuous high-energy AO bombardment. This mechanism prevents deep matrix penetration and successfully preserves a macroscopic optical transmittance of over 93% in the visible region. This study provides solid theoretical support and experimental evidence for designing highly reliable, long-life flexible protective coatings for aerospace applications. </p>