Local structural effects on thermodynamic properties and dynamic response

In this talk I will outline our recent progress in linking dynamic response of glassy materials to their thermodynamic properties which, in turn, link to local molecular structure. For example, the response of a bulk sample to an isothermal increase in pressure is slower segmental relaxation. We have shown this can be predicted using our independent equation-of-state analysis of thermodynamic data, which reveals both how the total volume and the free volume of the material change with pressure. Further, it turns out that an increase in total volume does not necessarily track with an increase in free volume. [1] Being able to deconvolute the two using a first principles theory is key to understanding the impact of local packing changes on dynamic response. The latter is tracked using our simple theory that exploits a rate model to capture both the volume and temperature dependence of segmental relaxation . I will focus on two kinds of systems that illustrate this thermodynamic-dynamic linkage: One comprises two sets of nanocomposites, the other a family of increasingly crosslinked polyvinylethylenes. This work has been supported through NSF-DMR-2006504.