Relaxation-Function-Dependent Two-Barrier Model for Nanoconfinement Effects on the Glass Transition

One of the central challenges in the study of nanoconfined systems has been the fact that distinct measures of these systems can report quantitative and qualitative differences in perturbations from bulk. This scenario has been further complicated by the recent observation in experiment of an apparent onset condition of nanoconfinement effects at temperatures only modestly above Tg. This observation has raised additional questions regarding the interpretation of large observed nanoconfinement effects in simulated systems at temperatures relatively much further above Tg. Here, using simulations and scaling theory, we show that this rich phenomenology can be unified via the combination of a two-barrier model of the glass transition with a barrier-truncation scenario for nanoconfinement effects. We discuss strong implications of these results for the viability of existing theories of the glass transition.