Fullerenes substituted with hydrophilic side groups form aggregates in aqueous solutions which are quite different from those formed by bare fullerenes. This difference can be a result of balance between hydrophobic and hydrophilic interactions. It is important to investigate factors those contribute to this balance in order to tailor the aggregation process. In this talk, I am going to present our recent molecular dynamics simulation study on phenyl-C60 -butyric acid methyl ester (PCBM) and an amphiphilic fullerene derivative (pyrrolidine-C60 cation) in water. We focused on the structure and dynamics of solvent molecules around the carbon nanoparticle. The translational as well as reorientational dynamics of water molecules in the first solvation shells of nanoparticles are remarkably slower than those in the bulk. There is a considerable difference in the structural arrangement and dynamic properties of water molecules in the first solvation shell of the hydrophobic part (C60) and those around the hydrophilic part (side chain). This anisotropy in solvation is more pronounced in the case of pyrrolidine-C60 cation. In our simulations in water, PCBM forms a nearly spherical aggregate whereas pyrrolidine-C60 cations cluster to form an arc-like aggregate. The difference in the aggregation of these two nanoparticles should be attributed to the delicate balance between several components of interaction in the system like hydrophobic attraction between C60 moieties, electrostatic interactions and some entropic effects due to counter-ions and solvent molecules.
Fullerenes substituted with hydrophilic side groups form aggregates in aqueous solutions which are quite different from those formed by bare fullerenes. This difference can be a result of balance between hydrophobic and hydrophilic interactions. It is important to investigate factors those contribute to this balance in order to tailor the aggregation process. In this talk, I am going to present our recent molecular dynamics simulation study on phenyl-C60 -butyric acid methyl ester (PCBM) and an amphiphilic fullerene derivative (pyrrolidine-C60 cation) in water. We focused on the structure and dynamics of solvent molecules around the carbon nanoparticle. The translational as well as reorientational dynamics of water molecules in the first solvation shells of nanoparticles are remarkably slower than those in the bulk. There is a considerable difference in the structural arrangement and dynamic properties of water molecules in the first solvation shell of the hydrophobic part (C60) and those around the hydrophilic part (side chain). This anisotropy in solvation is more pronounced in the case of pyrrolidine-C60 cation. In our simulations in water, PCBM forms a nearly spherical aggregate whereas pyrrolidine-C60 cations cluster to form an arc-like aggregate. The difference in the aggregation of these two nanoparticles should be attributed to the delicate balance between several components of interaction in the system like hydrophobic attraction between C60 moieties, electrostatic interactions and some entropic effects due to counter-ions and solvent molecules.
