Understanding the rheological behavior of polymer nanocomposites: Non-equilibrium thermodynamics modeling coupled with detailed atomistic non-equilibrium molecular dynamics simulations

Abstract

We describe a methodology for parameterizing and validating a continuum model for the rheological behaviour of polymer nanocomposites derived on principles of nonequilibrium thermodynamics based on numerical data collected from large-scale, fully-atomistic equilibrium (MD) and nonequilibrium molecular dynamics (NEMD) simulations. As a model system, we have chosen nanocomposites of polyethylene glycol (PEG) filled with functionalized silica (SiO 2 ) nanospheres. The parameterized continuum model provides a very satisfactory description of the simulation data for the conformational properties of the studied PEO-SiO 2 nanocomposite melts for a wide range of shear rates and SiO 2 concentration, as well and as with the viscometric functions in steady shear. It also fits quite accurately measured NEMD data for their viscosity as a function of shear rate except from the very high shear rates, also observed in the case of pure PEO melts. Possible ways to remedy this disagreement are proposed.