The properties of free polymer surfaces and their influence on the glass transition temperature of thin polystyrene films

Abstract.We present a detailed study of free polymer surfaces and their effects on the measured glass transition temperature (Tg) of thin polystyrene (PS) films. Direct measurements of the near-surface properties of PS films are made by monitoring the embedding of 10 and 20 nm diameter gold spheres into the surface of spin-cast PS films. At a temperature T = 378K( > Tg), the embedding of the spheres is driven by geometrical considerations …