Dynamics of a polymer nanocomposite under stress

The response of polymer glasses to deformation has received much attention in recent years. Previous simulation studies have shown that strain applied to a polymer glass can destroy energy barriers that impede relaxation on the potential energy landscape. However, less attention has been placed on the response of a polymer glass to an applied stress, as in a creep experiment. We have performed molecular simulations of the non-linear creep of a coarse-grained polymer glass and a polymer nanocomposite in shear, compression, and extension. We study the effects of the applied stress on the dynamics of our system and find dynamic enhancement up to a factor of 100 compared to the quiescent polymer glass below its glass transition temperature, Tg. We find that the free volume changes induced by the stress are not indicative of the changes in dynamics; however, the strainrate is strongly correlated with the dynamics.