Predicting Equilibration Dynamics of Polymer Confined at the Nanoscale via Material Time

Nonequilibrium phenomena are important in determining the dynamics of polymers confined at the nanoscale level. Growing experimental evidence demonstrates that nanoscale confinement giving rise to enhanced molecular mobility and deviation from the bulk behavior can be eliminated with time via very small density/volume changes that result from molecular rearrangements toward a more stable, i.e. less energetic, state. Remarkably, a similar effect is commonly observed upon physical aging of glasses. Here, we demonstrate that equilibration phenomena in nanopore confinement reveal the same fundamental features as the out-of-equilibrium response of (bulk) glasses subjected to various thermal histories. Following the concept of Narayanaswamy's single-parameter aging, we describe the equilibration of polymer dynamics at the nanoscale. The collected data show that the material-time concept is also valid in nanopore-confinement. Thus, it is possible to predict the confined polymer response to a temperature jump directly from the knowledge of a single relaxation curve.