Structural Relaxation of Polymer Glasses at Surfaces, Interfaces, and In Between.

We analyzed the glassy-state structural relaxation of polymersnear surfaces and interfaces by monitoring fluorescence in multilayerfilms. Relative to that of bulk, the rate of structural relaxation ofpoly(methyl methacrylate) is reduced by a factor of 2 at a free surfaceand by a factor of 15 at a silica substrate interface; the latterexhibits a nearly complete arresting of relaxation. The distribution inrelaxation rates extends more than 100 nanometers into the filminterior, a distance greater than that over which surfaces andinterfaces affect the glass transition temperature. [ABSTRACT FROM AUTHOR]