Tailoring and probing particle–polymer interactions in PMMA/silica nanocomposites†

The unique physical and mechanical properties of polymer nanocomposites have been attributed to the interfacial interactions between the organic matrix and nanoscale particles. We demonstrate the potential to tune this interaction between poly(methyl methacrylate) (PMMA) and silica nanoparticles, as a function of either nanosilica surface chemistry or polymer reactivity. Functionalized nanosilica was mechanically deposited on the surface of PMMA films, and the system then heated above the polymer glass transition temperature. Rates and extents of nanoparticle sink-in were quantified by timelapse atomic force microscopy-based imaging, showing that the strength of particle–matrix interactions was predicted directly by polymer–particle interaction energies. Nanocomposite films created via this approach exhibited significantly enhanced elastic moduli and scratch resistance. This direct quantification of mechanical optimization via nanoparticle–polymer interfacial chemistry enables new approaches to rapidly tune nanocomposite performance.