Dynamics of a Glassy Polymer Nanocomposite during Active Deformation

Abstract

We have examined the response of a polymer and a polymer nanocomposite glass to creep and constant strain rate deformations using Monte Carlo and molecular dynamics simulations. We find that nanoparticles stiffen the polymer glass, as evidenced by an increase in the initial slope of the stress−strain curve and a suppression of the creep response. In contrast to previous reports, we also find that, during deformation, the effective relaxation time or mobility of the material is only qualitatively characterized by the instantaneous strain rate. Constant strain rate and constant stress deformations have different effects on the material’s position on its energy landscape, and neither a mechanical variable, such as the stress or strain rate, nor a thermodynamic variable, such as the material’s position on its energy lanscape, is uniquely indicative of the relaxation times in the material.