Glass Transition Temperature Suppression and Free-Volume Distribution in Thin Polymeric Film Studied by Positron Annihilation Lifetime Spectroscopy

摘要

Glass transition temperature is one of the most important properties of thin film polymers or confined environment. A variety of techniques, such as Differential Scanning Calorimetry (DSC), Brillouin Light Scattering, Scanning Force Microscope (SFM), ellipsometry and fluorescence spectroscopy have been used to measure glass transition temperature of thin polymer films. However, despite much research efforts have been put on this area of research in recent years, the knowledge of the glass transition temperature in a thin film at different depth and interface is still not well established. One contributing factor to this difficulty is that very few methods can profile glass transition temperature as a function of the depth in thin polymer films.