Surface Dynamics in Polymer Nanocomposite Films*

The dynamics of supported polymer nanocomposite thin films were studied using x-ray photon correlation spectroscopy. Measurements were performed on 50 and 200 nm films of unentangled poly(2-vinyl pyridine) (P2VP) grafted gold nanoparticles in an unentangled P2VP host of smaller molecular weight at temperatures above the glass transition. The grafted and host chain degree of polymerization were $N=$96 and $P=$44 respectively. The presence of the nanoparticles and their interactions with the polymer host are shown to slow down the dynamics of the film at large thicknesses. As the film thickness $h$ approaches the interparticle spacing $l_{D}$, the dynamics become much slower due to confinement of the nanoparticles.