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 (SiO2) nanospheres. The parameterized continuum model provides a very satisfactory description of the simulation data for the conformational properties of the studied PEO-SiO2 nanocomposite melts for a wide range of shear rates and SiO2 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.