Effect of clay platelet orientation on spin cast nanocomposite films

The authors show that the thickness of spin cast nanocomposite polystyrene/clay films displays a large radial dependence that is not explained by current models. Transmission electron microscopy and atomic force microscopy reveal a tendency for the high aspect ratio clay particles to align in the direction of shear. Near the center of rotation, particles remain randomly oriented leading to the formation of voids as the film dries. They present a two dimensional numerical model that incorporates both hydrodynamic and orientation effects and accurately fits the thickness data over a wide range of filler concentrations and spin rates.