Interfacial properties of polystyrene thin films as revealed by neutron reflectivity

We have studied the glass transition temperature (T-g) and molecular mobility of polystyrene (PS) thin films near the interface between the polymer thin film and substratewith bilayer thin films consisting of surface hydrogenated PS (h-PS) and bottom deuterated PS (d-PS) using neutron reflectivity. With decreasing the thickness of the bottom d-PS layer, T-g near the interface between the polymer thin film and substrate increased compared to bulk T-g and a drastic increase of T-g was observed for the bottom d-PS layer < 155 angstrom thick. The orientation of polymer chains at the interface is supposed to be related to the increase of T-g near the interface between the polymer and substrate. The polymer chain mobility decreased with thickness even for the bottom d-PS layer with no discernible change of T-g. It is considered that the numerous contacts between polymer chains and substrate are related to the decrease of mobility near the interface between the polymer thin film and substrate.