Physics (Internal)

Thin film polymeric glasses: From top to bottom

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract:
Polymeric materials formulated as thin films can exhibit glass transition temperatures which are significantly shifted relative to bulk values. Depending on whether the film is supported (on a substrate) or freely-standing the temperature shift can go in different directions relative to the bulk. For all films the magnitude of the shift depends on film thickness. For supported films the shift appears to depend on substrate-polymer interactions, while for free-standing films there is a striking dependence on molecular weight. Experimental data published over the last few years have included some elegant and intriguing results which provide a significant challenge for those wishing to understand these phenomena. In this talk results from two models that predict both local and averaged film glass transitions in both free-standing and supported films will be presented. Model predictions will be discussed in the context of experimental data, and opinions regarding unresolved questions will be shared.