Tailoring the Morphology of Polymer-Grafted Nanoparticle Composites – A Study of Film Thickness and Nanoparticle Loading

Polymer nanocomposites (PNCs) provide solutions to various applications due to their enhanced material properties. These properties are intrinsically correlated with the dispersion state of the nanoparticles (NPs), which depends on various materials parameters and processing conditions. Our study aims to understand the PNC morphology and dynamics by varying parameters such as film thickness, nanoparticle loading, and annealing temperature. This study investigated PNC films of silica nanoparticles grafted with poly(methyl methacrylate) within a poly(styrene-ran-acrylonitrile) matrix. Using AFM and TEM, we investigated the surface and bulk structures of the PNC films after annealing. Additionally, water contact angle measurement and ToF-SIMS were used to assess surface hydrophilicity and quantify surface excess of the NPs. Unique domain growth patterns were observed for films of different thicknesses when examined through scaling laws relative to annealing time. We also constructed a bulk morphology map dependent on film thickness and annealing duration. At reduced loadings, the NPs were found to segregate to the surface upon annealing, leading to distinct particle-rich and particle-poor zones. This study demonstrates the interplay between thermodynamics, dynamics, and confinement in PNC films.