(192an) Molecular Simulations of Fullerene Stabilization in Water By Fullerene-Oxides

Making materials out of buckminsterfullerene is challenging because it requires first dispersing the molecules in a solvent, and then getting the molecules to assemble in the desired arrangements. In this computational work we focus on the dispersion challenge: How can we conveniently solubilize buckminsterfullerene? Water is a desirable solvent because of its ubiquity and biocompatibility, but its polarity makes the dispersion of nonpolar fullerenes challenging. We perform molecular dynamics simulations of fullerenes in the presence of fullerene oxides in implicit water to elucidate the role of interactions (van der Waals and Coulombic) have on the self-assembly and structure of these aqueous mixtures. Two coarse-grained fullerene models are characterized over a range of temperatures and interaction strengths using HOOMD-Blue on the Blue Waters supercomputer. For both models, we find temperature-dependent structural transitions and observe phases where fullerene oxides form a shell around droplets of fullerenes, which is consistent with experimental hypotheses for how the oxides help stabilize aqueous dispersions of fullerenes. This work demonstrates how high-throughput simulations help test experimental hypotheses while providing additional insight into molecular structure that is not easy to determine experimentally.