Structural Relaxation of Polymer Glasses at Surfaces, Interfaces, and In Between
Rodney D. Priestley,1
Christopher J. Ellison,1
Linda J. Broadbelt,1*
John M. Torkelson1,2*
We analyzed the glassy-state structural relaxation of polymers
near surfaces and interfaces by monitoring fluorescence in multilayer
films. Relative to that of bulk, the rate of structural relaxation
of poly(methyl methacrylate) is reduced by a factor of 2 at
a free surface and by a factor of 15 at a silica substrate interface;
the latter exhibits a nearly complete arresting of relaxation.
The distribution in relaxation rates extends more than 100 nanometers
into the film interior, a distance greater than that over which
surfaces and interfaces affect the glass transition temperature.
2 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
* To whom correspondence should be addressed. E-mail: broadbelt{at}northwestern.edu; j-torkelson{at}northwestern.edu
