Jammed Nanoparticle Structures in Polymer Nanocomposite Films Exhibit Improved Nanomechanical Properties

For poly(methyl methacrylate) grafted silica nanoparticles (PMMA-NP) and poly(styrene-ran-acrylonitrile) (SAN) films, unique polymer nanocomposite (PNC) morphologies are generated by controlling the interplay between surface enrichment, phase separation, and wetting. PMMA-NP:SAN films undergo distinct stages of phase evolution, resulting in homogenously dispersed systems, enriched PMMA-NP layers at the PNC interfaces, or three-dimensional bicontinuous structures. Using a combination of atomic force microscopy (AFM), AFM nanoindentation, contact angle goniometry, and optical microscopy, these self-regulated structures exhibit increased elastic modulus, hardness, and thermal stability compared to their analogous PMMA/SAN blends. These studies demonstrate the ability to reliably control surface-enriched and phase-separated nanocomposite microstructures to create coatings with attractive properties such as wettability, toughness, and wear resistance. In addition, these morphologies lend themselves to broader applications, including: (1) structural color applications, (2) tuning optical adsorption, and (3) barrier coatings.