A polymer dead layer is a very thin interfacial layer of polymer formed at the solid substrate interface, with no thermal expansion coefficient and molecular mobility. The polymer dead layer has many unique properties compared to the bulk polymer, including the mobility of polymer chains, glass transition temperature, viscosity and so on. In this thesis, organic clay nanoparticles are used as a nanofiller to see how the properties/structures a polystyrene dead layer can be altered. To characterize the structures of PS/clay dead layers, we used ellipsometry, X-ray scattering techniques, and atomic force microscopy (AFM). In addition, supercritical carbon dioxide was used as a screening solvent to control the polymer/substrate interactions.