Multiscale modelling of flow- induced crystallisation in polymers.

Presented by Richard Graham - School of Mathematical Sciences, University of Nottingham

Abstract: Applying flow to polymers can profoundly change how they crystallise. Flow enhances the crystal nucleation rate, often by orders of magnitude, and controls the shape and alignment of crystals. This externally driven, non-equilibrium phase transition is a key fundamental problem in polymer physics. It is also of great interest to the polymer processing industry. A quantitative understanding of flow-induced crystallisation would enable control of the properties of semi-crystalline products by tailoring flow conditions. However, simulating and modelling flow-induced crystallisation in polymers is notoriously difficult, due to the very wide spread of length and timescales. I will present results from a recent multiscale modelling project. Here, we used systematic multiscale modelling to integrate several different levels of modelling. This includes Molecular Dynamics simulations, highly coarse-grained kinetic Monte-Carlo simulations and continuum-level thermodynamic modelling. This results in a highly tractable model of flow-induced nucleation with deep-rooted molecular origins. Our model predicts that long chains are enriched in flow induced nucleation from polydisperse melts. In particular, the model shows that multiple chain lengths co-operate in non-trivial ways to create a critical nucleus. I will demonstrate quantitative support for this idea from both experiments and molecular dynamics simulations.