LAUSR

Abstract In the present work we accomplished analysis of interplay of enthalpic (van der Waals and electrostatic) and entropic (solvophobic) factors into the aggregation process of fullerene C60 in solution. We showed that in order to maintain the fullerene clusters stable their internal structure must be irregular, viz. dense packing of fullerene molecules inside (the nucleus) and loose packing on the outer shell. The stabilization of the nucleus is governed by van der Waals factor with negligible contribution from electrostatics, whereas the stability of the outer shell is mainly determined by electrostatics. We demonstrated, that the outer shell of clusters is made of the fullerene mantle with water molecules incorporated, required for reduction the electrostatic repulsion of surface charges. Such irregularity enabled to explain the origin of well-known intrinsic fractality of large fullerene clusters, the existence of barrier of solvent polarity required to maintain the clusters stable, and predicted the attenuation of the aggregation constant for large clusters. And, finally, we showed that fullerene binding to clusters is accompanied by small magnitude of van der Waals and electrostatic interactions, thus explaining the purely entropic character of fullerene aggregation with nearly zero experimental enthalpy change.