Unraveling MolecularEnhancement Mechanisms in VoltageStabilizer-Grafted Epoxy Insulation: Dielectric, Hygrothermal, andMechanical Perspectives

The escalating demand for high-voltage electrical insulation materials that can operate under extreme electric fields and thermal stress necessitates transformative approaches beyond conventional filler reinforcement strategies. Here, we present a covalent molecular grafting paradigm that integrates two distinct voltage stabilizers, 4-formylphenyl pentenoate (FP) and 4-maleimido-benzaldehyde (MB), into anhydride-cured bisphenol A epoxy (BisA-MTHPA) networks, achieving synergistic enhancement of electrical insulation, moisture resilience, and thermomechanical stability. Leveraging a synergistic multiscale computational hierarchy integrating first-principles electronic structure theory, statistical-mechanical Monte Carlo sampling, and reactive molecular dynamics, we elucidate the structure–property relationships governing charge trapping, molecular aggregation, and thermal degradation mechanisms. Our results demonstrate that FP and MB grafting introduces deep charge traps of 1.1 and 1.3 eV, respectively, effectively capturing high-energy electrons and suppressing electron avalanche multiplication, while the induced dipole moments enhance the effective electronic mass and reduce carrier mobility. The grafted moieties concurrently attenuate the C–H vibrational intensities by 11–14%, establishing supplementary thermal dissipation channels that mitigate localized heating and carbonized breakdown channel formation. Notably, FP grafting reduces the free volume density and H2O uptake through tighter coalescence of the EP molecular chain segments, whereas MB grafting imparts superior hydrophobicity and thermal stability, as evidenced by a 450 K elevation in the pyrolysis inception temperature. Both modifications substantially decrease thermal expansion coefficients and enhance the tensile elasticity, albeit with trade-offs in the high-temperature pyrolysis behavior. This molecular design strategy establishes a “charge trapping–moisture resilience–thermomechanical stability” triad enhancement mechanism, providing fundamental insights and predictive capabilities for developing next-generation polymer dielectrics capable of withstanding multifield aging in high-voltage power transmission systems and electric vehicle power modules.