{'fraction_non_alphanumeric': 0.025606469002695417, 'fraction_numerical': 0.012129380053908356, 'mean_word_length': 5.2133891213389125, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Adsorption Free Energies of Imidazolinium-Type Surfactants in Infinite Dilution and in Micellar State on Gold Surface.

We report adsorption behavior of imidazolinium-type surfactant molecules in different aggregation states on metal-water interfaces studied using all-atom molecular dynamics simulations. Surfactant molecules with two different alkyl tail lengths, a 10-carbon and a 17-carbon tail (henceforth referred to as imid-10 and imid-17, respectively), have been considered. Six layers of face-centered cubic lattice of gold atoms submerged in water represent the metal-water interface. Our simulations reveal that, in infinite dilution, both types of surfactant molecules strongly adsorb onto the metal-water interface in a configuration with their alkyl tail lying parallel to the surface. This adsorption occurs through a barrierless transition with an adsorption free energy of ∼30 kB T and is found to be enthalpically driven and entropically unfavorable. Surfactant micelles, on the other hand, experience a long-range repulsion from the metal surface at distances as large as 50-60 Å due to the presence of a large "corona" around the micelles that comprises counterions and their solvation layer. Surfactant micelles have an adsorption free energy barrier of ∼13-16 kB T, which is associated with the removal of adsorbed water from the metal surface. Micelles are thermodynamically stable in the bulk aqueous phase, and the adsorbed micellar state is only metastable.