Topographical Nanostructure Patterning on the Surface of a Thin Film of Polyurethane Containing Azobenzene Moiety Using the Optical Near Field around Polystyrene Spheres

Abstract

An indented nanostructure was formed on the surface of azobenzene-functionalized polyurethane thin films by the induced migration of polymer chains using the optical near field generated around polystyrene (PS) spheres. The PS spheres, which had a diameter ranging from 98 to 990 nm, were arranged on the surface of a photoresponsive polymer film using a self-organization process, and the films were then exposed to a linearly polarized Ar+ laser at 488 nm. A hexagonal array of indentations reflecting the original geometry and arrangement of the spheres was observed on the polyurethane surface by atomic force microscopy. The indented structure that was formed had a resolution of ∼95 nm. This structure was stable at room temperature and could be erased by heating the films above their glass transition temperature (Tg). The modification depth and diameter of the dents formed depended on the size of the original PS spheres. In particular, deeper dents were formed by using PS spheres with a diameter of over 505 ...