Prediction of Molecular Affinity on Solid Surfaces via Three-Dimensional Solubility Parameters Using Interfacial Free Energy as Interaction Threshold

Various adhesive and wetting phenomena in nature and practical applications originate from the interaction between the surfaces of materials and other substances. In this study, we developed a method for calculating the Hansen solubility parameters (HSP) of the surface of the solid materials to elucidate the surface interaction by quantitatively and visually representing adsorptivity with a three-dimensional vector. The HSP were derived from the interfacial free energy, which can easily be calculated from the contact angles of three organic solvents on the solid materials. The HSP for a glassy carbon (GC) surface calculated using our method were correlated with the adsorptivity on the GC surface of several organic molecules. The adsorptivity was evaluated using electrochemical impedance spectroscopy and molecular mechanics simulations; the latter of which also revealed that the HSP calculated for the Pt surface were highly correlated with its interactivity. Moreover, the HSP of the polytetrafluoroethylene (PTFE) surface obtained herein appropriately reflect the molecular structure of PTFE. The results underpin that our method enables the elucidation of various surface phenomena involving noncovalent interaction and allows the affinity between solid surfaces and tens of thousands of substances recorded in the HSP database to be predicted.