Graft Polymerization of Styrene on Mica: Formation and Behavior of Molecular Droplets and Thin Films

Cation-bearing peroxide free-radical initiators were attached to mica surfaces via ion exchange and used to polymerize styrene. Polystyrene chains grafted to the mica by growth from the surface resulted. Scanning electron microscopy showed distinct droplets on the surface. The droplets appear, from their size, to each consist of a single polymer chain molecule. The density of the droplets on the surface could be varied by varying the polymerization time. The droplets could be made to coalesce into thin films by increasing the grafting density, by heating, or by solvent treatment. Upon heating, the droplets appeared to spread on the surface at temperatures well below the normal glass transition temperature of polystyrene.