Nanoparticles with controllable dispersion and localization in immiscible polymer blends

Polymer blending is a versatile route to the development of new polymeric materials with enhanced properties and hence applications. However, the unfavorable interaction between most polymer pairs leads to phase-separated systems with unstable morphologies, weak interfaces and poor properties. The use of nanoparticles (NPs) as interfacial stabilizers has gained momentum recently due to their high surface area and strong adsorption at interfaces, but controlling their dispersion and localization in immiscible polymer blends is a major challenge. Recent work has demonstrated that polymer-grafted NPs, which exhibit surfactant-like properties, can self-assemble into a variety of superstructures that depend on the polymer grafting density (σ) and the graft chain length (N). Here, we will show that the location of polystyrene-grafted NPs within an immiscible blend of polymethyl methacrylate (PMMA)/polystyrene (PS) can be determined using σN^0.5, the brush crowding parameter, and, 1/α, which describes the entropic effects associated with a mismatch in brush/matrix polymer chain lengths. Using these parameters, the spatial control over NP segregation in immiscible polymer blends is probed and understood.