Asphaltene,which is considered as the heaviest and most polar component of heavy oil,can easily form aggregate structures.In order to get a deeper insight into the aggregation behavior,we use the macrocyclic aromatic conjugation system(MACS)to mimic the asphaltene molecules and the aggregation behaviors of MACS are investigated via the full atomic molecular dynamics(MD)simulations.It is found that the initially random-placed MACS self-assembled into some ordered nanoaggregates.According to the MD results,the stacking structure of nanoaggregates is affected by the number of aromatic ring in the conjugate system and the properties of side chain attached to the MACS.When the number of aromatic ring reached a certain value,MACSs are inclined to form highly crystalline phase that stack face-to-face orientation.Furthermore,we investigate the influence of aliphatic side chains on the crystalline structure and find that the crystalline asphaltenes form a columnar array.We also study the effect of solvent on the aggregation behaviors of the asphaltene.When the organic solvent molecules(such as dodecane)are added to the MACS,it resulted in an observably phase separation for the asphaltene aggregate.