Using molecular dynamics simulations to develop multiscale models of flow- induced nucleation in polymers.

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by Professor Prof Richard S. Graham - University of Newcastle

Using molecular dynamics simulations to develop multiscale models of flow- induced nucleation in polymers.

I will discuss how molecular dynamics have helped develop a recent multiscale model of flow-induced crystallisation in polymers [1]. 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 problem is simultaneously of great theoretical and industrial interest. However, simulating and modelling flow-induced crystallisation in polymers is notoriously difficult, due to the very wide spread of length and timescales.
I will discuss a recent modelling project. Here, we used systematic multiscale modelling to integrate several different levels of modelling[1]. 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.
Molecular dynamics simulations played a key role in both developing the model [2] and validating its predictions [3]. This was particularly important as the key process, namely nucleation, is too small and fast to be observed directly in experiments. I will discuss the computational difficulties with simulating this problem and how multiscale modelling helped alleviate these.

[1] Read DJ, McIlroy C, Das C, Harlen OG, Graham RS, PolySTRAND model of flow-induced nucleation in polymers, Physical Review Letters 124 (14), 147802 (2020)
[2] Anwar M and Graham RS, Molecular dynamics simulations of crystal nucleation in entangled polymer melts under start-up shear conditions, J. Chem. Phys. 150, 084905 (2019);
[3] Anwar M and Graham RS, Direct observation of long chain enrichment in flow-induced nuclei from molecular dynamics simulations of bimodal blends, Soft Matter 17, 2872-2882 (2021).
This seminar will take place via Zoom webinar
recording is here

Friday, July 9, 2021 - 11:00 to 12:00


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