Nanoparticle Assembly in Polymer Nanocomposite Films

In a phase separating polymer nanocomposite (PNC), the interplay between thermodynamic and dynamic behavior can be used to control the assembly of polymer grafted nanoparticles. Here, poly(methyl methacrylate) grafted silica nanoparticles (PMMA-NP) are mixed with a poly(styrene-ran-acrylonitrile) (SAN) matrix and characterized by a combination of surface (AFM, TOF-SIMS) and bulk (SAXS, TEM) methods. This talk will summarize three key findings. (1) For a PNC film (ca. 400nm) with 25 wt% PMMA-NP, a kinetically trapped structure with enhanced mechanical properties is fabricated. (2) The morphology and its evolution depend on film thickness and can be summarized in a morphology map. (3) Upon reducing the PMMA-NP composition to 10 wt% and annealing in the one-phase region, surface segregation of nanoparticles leads to the formation of particle rich and particle poor domains across the surface. These studies demonstrate the ability to reliably control surface-enriched and phase-separated nanocomposite microstructures to create coatings with attractive properties that can be tuned by the function of the chosen nanoparticle.