Multiscale approach to predicting the mechanical behavior of polymeric melts

Abstract

Modeling the mechanical behavior of polymers and polymer-based materials is notoriously difficult, primarily due to the need to integrate physics taking place on multiple scales. In this chapter we review single-scale models used to represent polymers and their composites, including atomistic, coarse-grained, and continuum models. Each of these has limitations associated with either accuracy or efficiency. To combine their advantages while reducing the associated drawbacks, multiscale methods are desirable. Two strategies are presented, both belonging to the class of information-passing methods. In the first, the physics of (dielectric and stress) relaxation is studied on the molecular scale and relevant parameters are calibrated using single-scale molecular dynamics and Monte Carlo techniques. These parameters are then incorporated in constitutive laws whose functional form is physically motivated. Such constitutive laws can then be used in continuum models on larger scales. This strategy is exemplified for a class of model polymer nanocomposites. In the second approach, a system reduction technology is developed to coarse grain the structure and dynamics of atomistic models of dense polymers. The coarse-grained models are calibrated using an equilibrium fine-scale model of a monodisperse system and then are used to predict the behavior of other systems in equilibrium and nonequilibrium. © 2009 Springer-Verlag US.