New breakthrough in interfacial characterization: concept of molecular surface area of molecules from a static geometric constant into a dynamic thermodynamic property using inverse gas chromatography

The accurate determination of the London dispersive surface energy (γ_s^d​) of solids is a fundamental challenge in interfacial science, with implications for adhesion, wetting, catalysis, and material design. Conventional approaches to estimate γ_s^d​ rely on molecular models that approximate the surface area of probe molecules, yet these models treat molecular surface area as a fixed, geometry-based parameter, ignoring its thermodynamic dependence on temperature and the nature of the solid substrate. In this study, we introduce a new method to determine the temperature-dependent molecular surface area of n-alkanes and polar solvents adsorbed on solid oxides. The approach combines the Hamaker constant formalism with the London dispersive interaction equation, as we recently reformulated, to separate dispersive and polar contributions to the adsorption free energy. By integrating molecular polarizability and ionization energy with experimentally derived γ_s^d, we obtain, for the first time, a consistent thermodynamic expression of the molecular surface area as a function of temperature. This method resolves long-standing discrepancies among classical molecular models, provides unprecedented accuracy in γ_s^d determination, and opens pathways to extend the analysis to polymers, fibers, and nanostructured materials.