Surface Dynamics of Dry Homopolymer Brushes

The dynamics of the surface height fluctuations on layers of covalently tethered, nearly monodisperse polymer chains synthesized by atom transfer radical polymerization were studied using X-ray photon correlation spectroscopy. The data reveal that both polystyrene and poly(n-butyl acrylate) brushes have structure at the Surface with length scales in the region of 620-3100 nm, but the surface features show no relaxation in a time window of 0.1...1000 s, even at temperatures more than 130 degrees C above the glass transition temperature of the corresponding untethered chains. This remarkable alteration of the dynamics, is compared with the suppression of fluctuations Oil this length Scale anticipated by thermodynamic theories. The alteration Of Surface dynamics by tethering has implications for wetting, friction, and adhesion.