Determination of Polymer Gel Viscoelasticity using Probe Rheology Simulations

In previous work, we showed that the viscoelastic moduli of unentangled and entangled polymer melts can be determined using the probe rheology technique in conjunction with molecular dynamics (MD) simulations. In order to assess the generality of the approach, we apply the technique to bead-spring models of polymer gel systems in this work. Active probe rheology simulations are carried out by subjecting a rigid particle that is embedded in a polymer gel matrix to an oscillatory external force. The observed probe motion is analyzed using the inertial generalized Stokes-Einstein relation (IGSER) to yield viscoelastic properties of the medium as a function of frequency. The results obtained by probe rheology simulations are compared with those obtained by the non-equilibrium molecular dynamics (NEMD) simulations. Results will also be presented for the effect of probe particle size and cross-link density of the gel on the observed viscoelastic properties of the gel medium.