Unraveling Aging Processes by Molecular Dynamics in High Impact Polystyrene/Organoclay Nanocomposites using Solid-State NMR to understand the microplastics generation

High-impact polystyrene (HIPS) nanocomposites containing organoclay were investigated under UV-accelerated aging using solid-state NMR to elucidate the evolution of molecular mobility and morphology. 13C CPMAS with variable contact time (VCT) and proton spin-lattice relaxation in the rotating frame (T₁ρH) sensitively captured the competition between chain scission and recombination across the nanocomposite films before and after exposure. The 1 wt% formulation predominantly displayed intercalated character with attenuated mobility changes upon aging, whereas 2-3 wt% systems showed heterogeneous and partially exfoliated morphologies with amplified mobility. While solid-state NMR does not directly detect microplastic particles, the relaxation signatures provide molecular-level evidence of fragmentation pathways with implications for potential microplastic formation.