High-Throughput Molecular Dynamics Simulations and Validation of Thermophysical Properties of Polymers

Recent advances in graphics-processing-unit (GPU) hardware and improved efficiencies of atomistic simulation programs allow the screening of a large number of polymers to predict properties that require running and analyzing long Molecular Dynamics (MD) trajectories of large molecular systems. This paper outlines an efficient MD cooling simulation workflow based on GPU MD simulation and the refined Optimized Potentials for Liquids Simulation (OPLS) OPLS3e force field to calculate glass transition temperatures (Tg) of 315 polymers for which experimental values were reported by Bicerano.1 We observed good agreement of predicted Tg values with experimental observation across a wide range of polymers, which confirms the clear utility of the described workflow. During the stepwise cooling simulation for the calculation of Tg, a subset of polymers clearly showed an ordered structure developing as the temperature decreased. Such polymers have a point of discontinuity on the specific volume vs. temperature plot, which we associated with the melting temperature (Tm). We demonstrate the distinction between crystallized and amorphous polymers by examining polyethylene. Linear polyethylene shows a discontinuity in the specific volume vs. temperature plot, but we do not observe the discontinuity for branched polyethylene simulations.