Trap State Modulation via Strong Electron-Withdrawing Groups for Enhanced Vacuum Surface Insulation of All-Organic Polyimide

Polyimide (PI), a high-performance polymer widely employed in aerospace applications due to its superior electrical insulation, processability, and long-term stability, faces operational challenges at vacuum-solid interfaces. Under extreme space conditions, vacuum flashover phenomena frequently occur at PI interfaces during spacecraft operation, critically jeopardizing the reliability of the onboard electronic components. This study demonstrates a molecular engineering strategy to suppress secondary electron emission and improve surface insulation by modulating trap states through strong electron-withdrawing groups. Two all-organic specialty PI films were systematically developed via a strategic molecular structure design and subsequently fabricated. These films incorporate strong electron-withdrawing groups (e.g., -SO₂- and -CF₃), which effectively enhance trap densities and deepen trap levels, thereby suppressing the secondary electron multiplication process. Both specialty PI films demonstrated significantly enhanced vacuum surface flashover thresholds, with their vacuum flashover voltages U_ho increased by 12.65 and 17.08% compared to pristine PI, respectively. The proposed molecular design paradigm provides a fundamental advancement in dielectric materials engineering, addressing the critical need for high-voltage tolerant insulation systems in next-generation spacecraft requiring elevated operational power and extended mission durations.