Near Surface Dynamics of Polymers Probed with Nanoparticle Embedding

We use nanoparticle embedding to probe the dynamics of the near surface layer of glassy polymer films. We observe evidence for heterogeneous dynamics in the first 5-10 nm near the free surface of glassy polymers. We observe that the relaxation into the polymer immediately below the free surface is irreversible, even after a period of 1 year. On the other hand, further embedding (5 -10 nm) appears to be reversible. The results are discussed in terms of posible models of near surface mechanical properties.