Solvent Effects on Osmotic Second Virial Coefficient Studied Using Analytic Molecular Models. Application to Solutions of C_(60) Fullerene

摘要

Osmotic second virial coefficients (OSVC's) are calculated analytically for some molecular models in which the solvent is taken into account explicitly. The basic effect of solvent packing is examined first by applying the method to the reference case of a binary hard sphere mixture. Then, cohesion forces for the solvent and solute-solvent attractive forces are introduced successively into the description. The results are applied to interpret recent experimental data on solutions of C_(60) in nonaqueous solvents. With a plausible assumption in the model, a very good agreement is obtained with the experimental OSVC value for C_(60) in CS_2. In the case of benzene as the solvent, the theoretical result is consistent with the experimental observation (formation of aggregates). No specific adjustable parameter was needed in the model to interpret the experimental results. The description suggests that the solute-solvent interaction has a determinant influence on the observed OSVC value.