2015-05-20
10:15 at HCI J 574

Complex flow predictions of highly entangled polymers

Jay Schieber

Illinois Institute of Technology

The Doi-Edwards tube model provides by far the most popular basis for a molecular model of entangled polymer dynamics. However, in order to provide reasonably quantitative agreement with observation, there have been many independent phenomenological additions to the model, such that there really is no single tube model, but rather different models for different kinds of flows, different chain architectures, or blends. Because of these limitations, we developed an alternative approach. We use a series of hypothesis-driven coarse-graining steps to create a hierarchy of integrated slip-link models. This procedure produces a mathematical model whose calculations are 3 million times faster than the most-detailed level of description, and 20 billion times faster than atomistic-level calculations. Using any single member of the hierarchy, we can then fit our single adjustable (friction) parameter to a dynamic equilibrium experiment of a single chain molecular weight and architecture, and make predictions of the nonlinear rheology of any chain architecture, molecular weight, blends of these and in any flow field. Predictions of experiment are quantitative. Porting of our code to GPUs gives an additional two orders of speedup, making most calculations possible on a desktop computer with a single graphics card. More important than computational speed up is the dramatic reduction in the number of dynamic variables necessary to describe the system, which suggests a deep understanding of the physics of entangled polymers, justifying the postulations made by Sam Edwards and Pierre-Gilles de Gennes more than 40 years ago.