Guan-Da Li, Hui Niu
Controlling the phase morphology of immiscible polyolefin blends, such as the isotactic polypropylene (iPP)/ethylene-propylene rubber (EPR) system, is fundamentally constrained by the trade-off between interfacial stability and melt processability, particularly under conditions of significant viscosity mismatch. Herein, we present a dynamic interfacial control strategy that reconciles these competing requirements via reversible aromatic associations. By introducing a small amount of 4-vinylbiphenyl onto both iPP and EPR chains through reactive extrusion, we establish dynamic π–π interactions across the phase interface. These interactions are sufficiently mobile to permit melt flow but strong enough to suppress coalescence, progressively refining the EPR domain size from 1.74 to 0.29 μm with increasing grafting content. Consequently, the room-temperature notched impact strength exhibits a 5-fold increase, accompanied by a pronounced brittle-to-ductile transition, while stiffness and melt rheology remain well-preserved. The toughening mechanism is attributed to the synergistic effects of refined rubber morphology and dynamically reinforced interfaces, which promote cavitation and extensive plastic deformation of the matrix. This work demonstrates that moderate, reversible supramolecular interactions offer a robust pathway for regulating the morphology and performance of nonpolar polymer systems without permanent cross-linking.