Thermomechanical and molecular interactions of adsorbed solvents on solid surfaces: A new method for separating van der Waals components

This work introduces a new methodology for quantifying and deconvoluting intermolecular forces governing the adsorption of organic molecules on solid oxides, using inverse gas chromatography (IGC) at infinite dilution. By combining high-precision retention measurements with a thermomechanical analysis framework, temperaturedependent adsorption energies, microscopic forces, surface stress, and deformation were systematically evaluated for a wide range of nonpolar and polar solvents interacting with silica surfaces. From these measurements, the Lennard-Jones potential parameters were directly determined, enabling a physically grounded description of the depth and range of adsorbate-surface interactions. A central advancement of this study is the first experimental separation of van der Waals contributions into their fundamental London dispersion, Debye induction, and Keesom orientation components. This correction reveals that the commonly used "polar" free energy of adsorption (Delta Gpa) systematically overestimates Lewis acid-base contributions by embedding large physical (nonLewis) electrostatic terms. The refined decomposition yields an accurate Lewis acid-base free energy, Delta GA-B consequently corrected donor-acceptor parameters for silica. The thermomechanical analysis demonstrates that the adsorption-induced surface stress decreases linearly with temperature, reflecting thermal relaxation of intermolecular forces at the interface. The combination of force decomposition, stress analysis, and LJ parameter extraction forms a coherent framework that links energetic, structural, and mechanical descriptors of adsorption. This integrative approach strengthens the molecular interpretation of IGC data and provides a transferable tool for characterizing surface energetics across oxide materials. Overall, the methodology advances fundamental understanding of solid-vapor interactions and offers practical relevance for the design of functional surfaces, nanomechanical sensors, chromatographic materials, and adsorption-based separation technologies.