Coarse-graining strategies for predicting properties of closely related polymer architectures: A case study of PEEK and PEKK

Sandipan Chattaraj,Sumit Basu

doi:10.1557/s43578-021-00332-0

Abstract

The ability of atomistic and coarse-grained models to discern between two polymers of very similar architecture is examined. To this end, polyether ether ketone (PEEK) and polyether ketone ketone (PEKK) are chosen. The difference in glass transition temperature and the similarity in compressive responses of the two polymers are captured by all-atom models. A coarse-graining scheme, with 6 beads per monomer and 3 types of beads, leads to a good approximation of the structure and packing of chains of PEEK and PEKK. The CG model reproduces differences in weakly rate-dependent properties such as {T}_{mathrm{g}}. Comparison between strongly rate-dependent uniaxial stress–strain responses of these two polymers requires a knowledge of the scaling between physical strain rate in one to the effective rate in the other. The scaling can be approximately determined by comparing the variation of yield strength with strain rate, obtained from small-sized simulations.Graphic abstract

Highlights

Coarse-grained (CG) molecular dynamics (MD) simulations are increasingly playing an important role in our efforts to understand how macroscopic properties of glassy polymers depend on their molecular architecture
The glass transition temperature of polyether ketone ketone (PEKK) is 160 ◦C compared to 147 ◦C for polyether ether ketone (PEEK)
CG MD simulations of long chained amorphous, glassy polymers can be used for predicting their mechanical properties

Summary

Introduction

Coarse-grained (CG) molecular dynamics (MD) simulations are increasingly playing an important role in our efforts to understand how macroscopic properties of glassy polymers depend on their molecular architecture. Such understanding takes us closer to the important technological goal of designing the architecture to achieve a set of targetted macroscopic properties. Journal of Materials Research 2021 www.mrs.org/jmr interaction centres in computations. This has the potential to extend the time scale significantly and the length scale modestly when MD computations are conducted with the CG polymer. CG MD simulations have enabled researchers to investigate problems such as polymer indentation [16], mechanics of crosslinked amorphous polymer adhesives [17], mechanical behaviour of polymer thin films [18], and thermomechanical properties of bulk polymers [19]

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