A Direct Quantitative Measure of Surface Mobility in a Glassy Polymer

Abstract

Polymer Film Behavior An ongoing debate in the understanding of the behavior of thin-film glassy polymers is whether there is nanoconfinement of large molecules or enhanced mobility near a free surface. Chai et al. (p. 994 ; see the Perspective by Chen et al. ) prepared polymer films with a sharp step in the profile by depositing broken film fragments onto a uniform underlay. Atomic force microscopy revealed changes to the overall film profile with time at various temperatures. A transition was observed from localized motions to relaxation of the entire film at a temperature close to that of the bulk glass transition temperature.