Molecular dynamics study of loading-dependent glass transition and thermal-stability-related properties in ZrO₂/PMIA and fluorinated graphene/PMIA nanocomposites

To investigate the effect of nanofiller dimensionality on the thermal stability of poly(m-phenylene isophthalamide) (PMIA) insulating films and the underlying mechanisms, zero-dimensional ZrO₂ nanoparticles and two-dimensional fluorinated graphene (FG) were selected as representative fillers. Molecular dynamics simulations were performed on neat PMIA, ZrO₂/PMIA, and FG/PMIA nanocomposites with different filler loadings. The glass transition temperature, mean square displacement (MSD), interfacial binding energy, and free volume fraction (FFV) were calculated to evaluate glass-transition behavior and its associations with molecular mobility, interfacial energetics, and free volume. The simulations predict higher Tg values for the investigated composite models than for neat PMIA, with filler-dependent differences in molecular mobility and packing. The glass transition temperature of neat PMIA was 539 K, which increased to 578 K for 1 wt% ZrO₂/PMIA and 593 K for 3 wt% FG/PMIA. The MSD results showed loading-dependent differences in PMIA atomic mobility, with the relative mobility of the composite models varying with temperature. The combined results suggest associations between filler–matrix interactions, molecular packing, and restricted PMIA motion. For the nominal 1 wt% ZrO₂/PMIA and 3 wt% FG/PMIA models, the reduced FFV values indicated a smaller fraction of geometric free space. The combined analysis of FFV, MSD, and Tg revealed filler- and loading-dependent relationships among structural packing, atomic mobility, and glass-transition behavior. These findings provide molecular-level insight into the glass-transition behavior of the modeled PMIA nanocomposites and identify candidate filler loadings for further investigation.