Mechanistic Study of Atomic Oxygen Erosion on Polyimide Under Electric Fields: A Molecular Dynamics and Density Functional Theory Approach.

Polyimide (PI) is widely used in aerospace applications due to its superior insulating properties. However, the high concentration of atomic oxygen (AO) in low Earth orbit leads to significant performance degradation in PI, and the underlying mechanism of AO erosion under an electric field remains unclear. This study utilizes molecular dynamics simulations to model AO erosion on PI under various electric field strengths and explores the corresponding degradation mechanisms. The results indicate that the presence of an electric field exacerbates the degradation of PI by AO. AO erosion elevates the polymer's temperature, and the combined effects of thermal and electric stresses increase the polymer's free volume, loosening its structure and accelerating degradation. The quantity of AO-induced erosion products increases with rising electric field strength, causing more large carbon chains to detach from the polymer surface. Density functional theory (DFT) calculations further reveal that the electric field reduces the frontier orbital energy gap in PI molecules, making AO erosion reactions more thermodynamically favorable. This work provides an atomic-level insight into the degradation mechanism of PI under AO erosion in electric fields and offers a theoretical basis for future studies on polymer resistance to AO erosion in space environments.