Surface thermodynamic properties of [C_nMIM][MeSO₄] ionic liquids determined by inverse gas chromatography with...

Surface thermodynamics of [CMIM][MeSO₄] (n = 2, 4, 6, 8) ionic liquids were investigated by inverse gas chromatography at infinite dilution over 313.15-353.15 K. Three calculation approaches were compared for the dispersive surface energy (γ_d^s): the conventional Schultz method, the Dorris-Gray method, and the Schultz method with Hamieh's temperature-dependent molecular area correction. Lewis acidity-basicity constants (K_A, K_B) were derived by the Brookman-Sawyer, Flour-Papirer, Donnet-Park, and Schultz approaches within the Gutmann framework, and interpreted at the molecular level by ESP analysis based on the Murray-Politzer framework. The three γ_d^s methods exhibited distinctly different temperature dependences: the Dorris-Gray method gave the smallest temperature coefficient, the conventional Schultz method was intermediate, and the Hamieh-corrected Schultz method showed the largest. The relative magnitudes among the three methods varied with temperature, with the Schultz and Hamieh values converging at elevated temperatures. The four Lewis acid-base approaches gave consistent rankings of apparent surface basicity in the order Brookman-Sawyer > Schultz > Flour-Papirer > Donnet-Park, with all four ionic liquids exhibiting amphoteric Lewis behavior dominated by basicity, decreasing in the order EMIM > BMIM > HMIM > OMIM with increasing alkyl chain length. The complementary ESP analysis provided convergent evidence for the [Formula: see text] anion as the dominant Lewis basic surface feature. Adsorption free energies ranged from approximately 22 to 43 kJ/mol, consistent with physisorption with partial specific interaction contributions.