Effects of entanglement concentration on Tg and local segmental motions.

The process of spin-coating to fabricate thin polymer films with high molecular weight can produce samples with entanglement concentrations that are far below the equilibrium value. It is not clear whether or not such low entanglement concentrations are responsible for the depression of the glass temperature in thin polymer films. In this work, we measure the calorimetric glass temperature and viscoelastic response of polystyrenes with molecular weights ranging from 3x10(3) to 43.7x10(6) g/mol, for both bulk material and for samples freeze-dried from dilute solution. We conclude that the reduction of the glass temperature observed in thin polymer films cannot be due to the reduced entanglement concentration in the samples.