Benoit Schnell

Multiscale Modeling Approach toward the Prediction of Viscoelastic Properties of Polymers

We report a multiscale modeling approach to study static and dynamical properties of polymer melts at large time and length scales. We use a bottom-up approach consisting of deriving coarse-grained models from an atomistic description of the polymer melt. We use the iterative Boltzmann inversion (IBI) procedure and a pressure-correction function to map the thermodynamic conditions of the atomistic configurations. The coarse-grained models are incorporated in the dissipative particle dynamics (DPD) method. The thermodynamic, structural, and dynamical properties of the cis-1,4-polybutadiene melt are very well reproduced by the coarse-grained DPD models with a significative computational gain. We complete this study by addressing the challenging question of the investigation of the shear modulus evolution. As expected from experiments, the stress correlation functions show behaviors that are dependent on the molecular weights defining unentangled and weakly entangled polymer melts.

Prediction of structural and thermomechanical properties of polymers from multiscale simulations

We report mesoscale simulations of polymer melts and crosslinked polymer networks by using realistic coarse-grained (CG) models that are developed from atomistic simulations of polymer melts. We apply this multiscale strategy to different polymers in order to predict quantitatively some structural and thermomechanical properties such as the melt density, the end-to-end distance, the entanglement mass and the plateau modulus. The temperature dependence of the CG models is investigated through the calculation of the melt specific volumes at different temperatures and the calculation of the isothermal compressibility gives some insight into the pressure transferability of the CG models. We also show that the CG models can be applied successfully to high molecular weight chains. We test the performance of the CG models by calculating directly the plateau modulus of a crosslinked PIB network from mesoscopic simulations under a tensile stress. We compare the value of the plateau modulus with that calculated from the autocorrelation of the stress tensor during equilibrium simulations.