(573e) Rheological Characterization of Polymer Networks and Heavily Entangled Polymer Melts Using Particle Rheology Simulations

Determination of local viscoelastic moduli of polymer networks and entangled polymer melts is essential for many practical applications, such as tissue engineering and design of polymer nanocomposites. The particle rheology simulation technique, which combines molecular dynamics (MD) simulations with the inertial generalized Stokes-Einstein relation (IGSER), and is similar to the experimental microrheology technique, was previously employed to predict accurately the viscoelastic properties of unentangled (N < N_e (where, N_e = entanglement spacing)) and weakly entangled (N ~ N_e) polymer melts. In this work, we evaluate the generality of the particle rheology simulation technique by applying it to the rheological characterization of heavily entangled polymer melts with N > 10 N_e and polymer network systems of varying strand lengths, using probe particles of different sizes.

The passive and the active particle rheology simulation results are compared with those obtained noneqilibriummolecular dynamics (NEMD) simulations, and are discussed in the context of literature theories of particle motion in entangled environment, as well as in the context of interplay of various important characteristic length scales such as probe particle and network mesh size, and entanglement spacing. Our findings indicate that the viscoelastic moduli values obtained by probe rheology show a significant dependence on the size ratio of the probe and polymer structural length scales.