Non-linear Deformation of Polymer Grafted Nanoparticles

The linear viscoelastic properties of polymer-grafted nanoparticles indicate that they behave like elastic solids with elastic moduli that scale (non-linearly) with concentration of the nanoparticles (or grafting density) and with the molecular weight of the polymer chains grafted to the particles. We studied the non-linear viscoelastic properties of such polymer grafted nanoparticle melts through a systematic examination of step strain measurements, steady shear behavior and the recovery after cessation of steady shear flow. These materials exhibit a yield-strain that is grafting-density and molecular-weight independent. The local re-arrangement of particles and the formation of slip-planes and the regeneration of local order upon cessation of flow dominate the flow and recovery properties of these nanocomposites.