Engineering a Bimodal Multicore Dispersed Phase Structure for Low-Temperature Toughening of Polymer Nanocomposites

Polymer nanocomposites (PNCs) are often constrained by inadequate nanoparticle dispersion, weak interfacial interactions, and the resultant deterioration in melt processability and low-temperature brittleness. Herein, we fabricate a polypropylene/polystyrene-b-ethylene-propylene-b-polystyrene/ethylene-propylene rubber/nanosilica (PP/SEPS/EPR/SiO2) composite with a controllable bimodal-distribution multicore (BDM) structure using polystyrene (PS) as a nanogrinding medium. The PS nanodomains are found to effectively break up the agglomeration of SiO2 nanoparticles and hinder their migration to the interface, leading to the selective localization of SiO2 within the dispersed phase of the BDM structure. This enhances the process flowability and significantly strengthens the cavitation-suppressing effect of the complex dispersed phase. Based on this mechanism, the BDM structure delays craze propagation, improves impact-bearing capacity, and increases total energy absorption at low temperatures, all without significant compromise in strength. By constructing more sophisticated dispersed-phase structures and controlling the directional distribution of nanoparticles, this work provides an efficient, low-consumption strategy for producing PNCs with superior low-temperature toughness.