Experimental Relaxation Behavior and the Role of the α- Process and the Slow Arrhenius Process (SAP): Exploring Evidence, and Insights from Thermodynamic Analysis

Molecular level processes are important in driving the relaxation and equilibration of glass-forming materials. Here we consider two of them: the "segmental" α- relaxation process, and another, slower, Arrhenius-like process, the "SAP". Both can be tracked using dielectric spectroscopy. The α- process is well-known for its association with glassy behavior. However, it is common to find experimental behavior (e.g. equilibration kinetics, stress relaxation, etc.) that does not track with it, and in these cases, these observables often appear to be driven by the SAP. In this talk we will survey some of the most recent experimental evidence showing the appearance of the SAP, which can include various types of rheological measurements, physical aging, crystallization, adsorption, dewetting, and even lipid transfer. We will also discuss our recent modeling applications which can predict relaxation dynamics based on analysis of a material's thermodynamic properties.