Background: Graphene tends to form irreversible agglomerates or even restack to form graphite through attractive van der Waals interactions. Hence, finding a suitable solvent for dispersing graphene is very difficult. Hernandez et al. [1] showed the solubility parameter (δ) and surface tension are most important properties to find efficient solvents for dispersing graphene sheets. They stated best solvents for graphene should possess δ∼23 MPa1/2. In spite of the experimental work on measuring the solubility parameter of graphene, a molecular understanding of the solubility of graphene in different solvents has not been developed. The present study aims at investigating solubility parameter of graphene as functions of both the number of layers and temperature by molecular dynamics (MD) simulations. Methods: MD simulations with NPT and NVE ensemble were carried out using DL_POLY 2.17 package [2] to calculate the solubility parameter of graphene as function of the number of layers. The graphene layer contained 351 carbon atoms. The Tersoff-Brenner force field was employed to describe the interactions among the atoms. Results: As Fig. 1 shows, the solubility parameter of graphene increases with increasing the number of layers at constant temperature. Number of layers 1 2 3 4 5 6 7  (MPa1/2) 22 24 26 28 30 32 34 36 38 40 Fig. 1 Solubility parameter of graphene vs. the number of layers at 293.15 K Conclusion:  For the first time, we computed solubility parameter of graphene as functions of both the number of layers and temperature by molecular dynamic (MD) simulations  The solubility parameters of graphene increase with increasing the number of layers at constant temperature. Keywords: Graphene; solubility parameter; simulation; molecular dynamics References [1] Hernandez Y., Lotya M., Rickard D., Bergin S. D., Coleman J. N., Langmuir, 2009, 26, 3208-3213. [2] Smith W., Forester T., The DL_POLY package of molecular simulation routines, UK: Daresbury, 1996.

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