Aggregation of polyaromatic (PA) compounds has drawn great interest due to their wide impacts in areas such as petroleum processing. Despite the extensive studies on PA compounds, fundamental knowledge of their aggregation behaviors is still missing at atomistic level. For instance, it’s still unclear how the properties of the solvent can lead to different aggregation mechanisms and hence affect the aggregated structures of PA molecules.

In this dissertation, a series of molecular dynamics (MD) simulations have been performed to investigate the effect of solute chemical structures as well as solvents on the aggregation of PA compounds. The PA molecules studied here possess the same PA core structure but have systematically varied side-chain lengths. We started with simulating a single type of PA compounds in water. Inside the aggregated structures, while some PA core stacking was observed, most of the PA molecules are simply entangled together without preferred orientations. More interestingly, it was found that side-chain length has a non-monotonic effect on the size of the aggregates, with intermediate side-chain length leading to smaller aggregates. In contrast, regardless of the side-chain length, these PA molecules aggregated into ordered structures in toluene and 𝑛-heptane, which mainly consist of stacked PA cores. On the other hand, the ranges of stacking of PA cores in these two organic solvents are different, thus resulting in distinct aggregated geometries. Following the above studies which involve only a single type of PA compounds as the solute, we explored the aggregation of mixed PA compounds of different types in toluene, 𝑛-heptane and heptol (toluene/𝑛-heptane mixture). It was found that the inhomogeneity in solutes can enhance the stacking of PA cores, leading to the long-range stacking of PA cores. Furthermore, the existence of this long-range stacking of PA cores is insensitive to the solvents employed. Through detailed analysis of the aggregated structures, the aggregation mechanisms of different kinds of solutes were clarified. This dissertation provided insights for the aggregation of PA compounds from atomic level, and shed lights on controlling their aggregated structures.