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

Recent
advances in graphics processing unit (GPU) hardware and
improved efficiencies of atomistic simulation programs allow for the
screening of a large number of polymers to predict properties that
require running and analyzing long molecular dynamics (MD) trajectories.
This paper outlines a MD simulation workflow based on GPU MD simulation
and the refined optimized potentials for liquid simulation (OPLS)
OPLS3e force field to calculate glass transition temperatures (Tgs) of 315 polymers for which Bicerano reported
experimental values [Bicerano, J. Prediction of Polymer
Properties; Marcel Dekker Inc.: New York, 1996]. Applying the workflow across this large set of polymers allowed
for a comprehensive evaluation of the protocol performance and helped
in understanding its merits and limitations. We observe a consistent
trend between predicted Tg values and
empirical observation across several subsets of polymers. Thus, the
protocol established in this work is promising for exploring targeted
chemical spaces and aids in the evaluation of polymers for various
applications, including composites, coatings, electrical casings,
etc. 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 associate 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.