Nonlinear response to probe vitrification


Project P5

Molecular Dynamics simulations of active micro-rheology of glass-forming polymer melts


We will study the nonlinear response of supercooled polymer melts and glasses to local perturbations by means of Molecular Dynamics simulations. The perturbations will be applied, e.g., by pulling a probe particle through the polymer matrix, oscillating several particles within the matrix, or by inserting a dumbbell in a high energy state into the matrix. In the first two cases the stationary response of the melt is studied and in the third case the transient state with its nonlinear relaxation and dissipation of the stored energy is investigated. In all cases, the spatially resolved response of the polymer matrix to the perturbation will be determined, including structural changes and nonlinear flow response. Compared to colloidal or molecular fluids, polymers introduce additional length and time scales by the radius of gyration of the chains and the time for conformational relaxation, and the nonlinear response of the polymeric degrees of freedom will also be investigated.