Stability of polymer glasses vitrified under stress.

How stress or strain imparts mobility to glasses is a scientific issue linking ideas of jamming and the glass transition across colloids, granular materials, polymers, and molecular glasses. Here, we address for the first time how stress applied during vitrification, formation of the glassy state by a temperature quench, affects the subsequent stability of the glassy state, even after the stress has been removed. Using entangled polymers that are easily manipulated mechanically above the glass transition temperature, we find that the resulting polymer glasses become less stable, exhibiting a higher physical aging rate, when stress is applied while rapidly cooling the polymer films. The data show an initial plateau value at low stress, before transitioning rapidly to a higher aging rate at larger stress. These results are suggestive of the glassy system being left trapped in a less stable, higher energy state with faster physical aging rate when stressed above some minimum value during vitrification.