Simulation of graphene nanoribbon aggregation and its mediation by edge decoration.

Large polyaromatic molecules, including synthetic graphene nanoribbons (GNRs), are the subject of considerable interest for a variety of electronic applications. For GNRs in particular, functional groups can be bonded along the ribbon edges to modify their dispersibility, self-assembly behavior, and electronic properties. However, these side chains are usually chosen in a "trial and error" fashion, without an underlying molecular-scale picture of the conformations they will adopt in solution and the resulting influence of such structures on macroscopically observable phenomena, particularly aggregation. In this study, we use molecular dynamics (MD) to predict the behavior of various side chains in different solvents as a means to understand how this influences aggregate morphologies and binding energies. Specifically, oligomeric PEG and n-alkoxy chains of varying lengths and grafting densities are examined in vacuum, water, and N-methylpyrrolidone. Examining the binding energies and side chain dispositions that occur with different sets of parameters allows us to suggest a combination of these variables that will minimize aggregational tendencies for the GNRs. The results underscore the value of molecular-scale computational techniques to understand the aggregational tendencies of 2D materials and guide the design of future polyaromatic edge modifications.