Pressure-Resolved Molecular Dynamics of Transient SF6 Accumulation at Prescribed-Charge Polyimide Interfaces

Charge accumulation at polyimide (PI)/sulfur hexafluoride (SF6) boundaries can reorganize the molecular environment of gas-insulated equipment, yet near-surface population is often treated as a single adsorption response. We used atomistic molecular dynamics to resolve three distinct quantities at static surfaces of four 4,4′-oxydianiline-based PIs: gas loading, reservoir-referenced interfacial partitioning, and right-censoring-aware molecular residence. A matched, sign-swapped bipolar design combined real-fluid 5–20 atm reservoir states with charge-scale, duration, energy-decomposition, model-form, and finite-cell controls. Neutral loading increased the absolute interfacial population but reduced enrichment relative to the distal gas at 20 atm. The amplified perturbation produced PI-model- and loading-dependent surface-excess responses, while residence changes remained small and followed no common population trend. Literature-scaled charge densities were below the trajectory-level resolution, and 300 ps extensions showed that the initially resolved contrasts were transient rather than persistent cross-model rankings. An evidence hierarchy prevents supplied amount, spatial preference, and molecular persistence from being collapsed into one adsorption metric. It provides a reproducible molecular screening framework for comparing SF6-facing polymer interfaces and a quantitative benchmark for future polarizable, flexible-interface, and coupled-field studies.