Spatiotemporal Monitoring of the Simultaneous Migration and Aggregation of Inorganic Fillers in Polymers.

Inorganic fillers integrated into the polymer matrix were driven to aggregate and migrate as a balance of entropic and enthalpic contributions, leading to improved or decayed performances in polymer composites. However, current characterizations failed to provide a spatiotemporal and nondestructive evaluation of the simultaneous migration and aggregation of inorganic fillers within polymers. Herein, we have provided a spatiotemporal evaluation of the migration and aggregation of inorganic fillers within polymers through three-dimensional fluorescence imaging. The migration from the internal regions to the surface and aggregation in three dimensions have been simultaneously visualized. Quantitative evaluation has been implemented by taking particle number percentage at different depths for migration and nearest interparticle distance for aggregation. A dynamic variation F, considering the comprehensive effects of aggregation and migration, was established. This F was dependent on particle size in the time dimension: smaller particles exhibited greater tendencies for migration and aggregation with treatment time. More importantly, this comprehensive F was positively correlated with the performance decay of polymer composites. Therefore, this study has unveiled the migration and aggregation behaviors of inorganic fillers, explaining how cooperative interactions between polymer chains and inorganic fillers can lead to macroscopic behavior variations. It is believed that this study could provide useful guidance to tailor the performance of polymer composites.