Thermodynamics of Binding of Charged Dendrimers to Graphene: Simulation and Theory

The thermodynamics of the binding of a charged dendrimer [poly(amidoamine)] to an uncharged graphene sheet is investigated through simulations and a mean-field theory. A non-monotonicity that is observed in the degree of binding of the dendrimer as a function of pH is explained through potential of mean force (PMF) calculations and the Flory-Huggins-Debye-Huckle type mean field theory, by analyzing the electrostatic and non-electrostatic interactions between the pairs of dendrimer, graphene, and water molecules and ions. The simulation trends are satisfactorily reproduced by the theoretical results. In addition to the van der Waals interactions between the dendrimer and the graphene sheet, it is found that the presence of the solvent ions and counterions too has a major influence on these trends.