Molecular Weight-Directed Interfacial Localization of Polystyrene-Grafted Silica Nanoparticles for Compatibilizing Polyamide 6/Polycarbonate Blends

The performance of polyamide 6/polycarbonate (PA6/PC) blends is fundamentally limited by their thermodynamic immiscibility and weak interfacial interactions. Nanoparticle-based compatibilization offers a promising solution, yet achieving reliable interfacial localization remains a critical challenge. Here, we demonstrate that precise control over the molecular weight of polystyrene grafts on silica nanoparticles (SiO 2 -g-PS) enables selective interfacial localization and effective compatibilization in immiscible PA6/PC blends. Nanoparticles bearing short PS grafts tend to aggregate, whereas excessively long PS grafts preferentially disperse in the PC phase. In contrast, an optimized graft molecular weight (Mn ≈ 1.1 × 105 g/mol) favors localization at the PA6/PC interface, driven by stacking interactions as supported by density functional theory (DFT) calculations. This interfacial localization markedly refines the blend morphology, reducing the average diameter of the dispersed PC phase from 2.64 μm to 0.67 μm, and simultaneously enhances tensile strength and ductility. This work provides molecular-level guidance for the rational design of nanoparticle compatibilizers in immiscible polymer blends.