More Relaxed on the Surface

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Science  01 Feb 2008:
Vol. 319, Issue 5863, pp. 545c
DOI: 10.1126/science.319.5863.545c

The glassy state of materials, in which a liquid-like structure is frozen in place below a specific temperature, may manifest differently in the bulk of the materials versus the surface region. Fakhraai and Forrest (p. 600; see the Perspective by Dutcher and Ediger) probed the glass transition in an amorphous polymer by embedding gold nanoparticles onto the surface of a polystyrene film and allowing them to sink into the film, where they make small indentations. They then removed the gold, using mercury, and were able to watch the surface relaxation at various temperatures. They observed enhanced surface relaxation, that is, greater mobility of the polymer chains, at the surface relative to the bulk.

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