(774d) Enhanced Diffusion and Rejuvenation In Strained Glassy Polymer

A glassy material is in a non-equilibrium  state, and slowly moves toward the nearest equilibrium state. This process is called aging, and leads to changes in the material properties over time. Straining glassy materials have been postulated to 'rejuvenate' material properties (e.g., creep compliance), and recent experiments by Ediger and co-workers show that straining also leads to orders-of-magnitude enhancement in the dynamics (e.g., diffusion rates). We investigate this phenomenon using molecular dynamics simulations on a coarse grained model of polystyrene. Following strain, our results show that the dynamics of the material are accelerated, and become similar to the dynamics of equilibrium liquid near Tg. The enhancement in dynamic fades away with time and the behavior approaches that of the un-strained glass. The rate at which this enhancement fades away is shown to follow a powerlaw scaling, and is a function of both aging time and time-interval of measurement.