“…These changes can cause severe modifications to the local compressibility and molecular arrangements . Separately, there are tendencies for the chain ends, which possess more free volume than chain segments do, to segregate to the free surface and for the density of chain entanglement near the surface to be smaller than that in the bulk. ,− All of these factors can lead to enhancements in the near-surface mobility ,, and reductions in the T g of thin polymer films ( T g film ). − ,,, On the other hand, the surface chemistry ,,− and stiffness of the substrate supporting the films, and the near-substrate chain conformations , can affect the dynamics of the nearby polymer. Combinations of the free surface and substrate effects can produce a variety of thickness dependences of the thin film dynamics as found in experiments. ,,,, …”