Fluorescence Evidence That a Phase Transition Causes the Induction Time in the Reduction in Dynamic Tension during Surfactant Adsorption to a Clean Air/Water Interface and a Kinetic–Diffusive Transport Model for the Phase-Induced Induction

Phases and phase transitions in Gibbs monolayers of an alkyl phosphate surfactant

“…Surface pressure was then followed with time, and simultaneously the change in surface morphology was observed by BAM. explanation is that the induction time during adsorption of a surfactant is caused by a first-order phase transition from a gaseous state to a higher density phase [10][11][12][13]47,48]. After the induction time, the surface pressure rises with time, indicating that continuous adsorption of the molecules takes place during the experiment.…”

“…Any conspicuous cusp point in these π -t curves indicates a first-order phase transition [5][6][7][8][9]. Most claims of first-order phase transition in Gibbs monolayers are based on the existence of such a cusp point in the π -t curves followed by a plateau or on the surface tension relaxation in the γ -t curves [10][11][12][13]. Although, previously, there were some controversies over the existence of phase transitions, a first-order phase transition from a lower density state to a higher density state in Gibbs monolayers is now well established [5][6][7][8][9][10][11][12][13][14][15].…”

“…Considering the low solubility of surfactants showing phase transitions, Subramanyam and Maldarelli [11] took another nonionic surfactant with a large head group, hexa-(ethylene glycol) mono-n-tetradecyl ether. This head group increases the solubility of the amphiphile in water.…”

Interaction of an organic cation with Gibbs monolayers of n-hexadecyl phosphate

“…Several research groups, including ours, have studied the phase behavior of slightly water-soluble surfactants in these monolayers. These studies reveal that depending on the nature of the surfactants and the experimental conditions, first-order G-LC [23,24], G-LE [24][25][26][27] and/or LE-LC [27][28][29][30][31][32] phase transitions occur in the adsorbed monolayers at the air-water interface. The existence of a first-order phase transition in these monolayers is indicated by the appearance of a plateau or a cusp point followed by a plateau in the surface pressure (π )-time (t) isotherms.…”

“…One important factor that has not been studied in any detail, despite its obvious importance for surfactants capable of forming LC phases, is the effect of the counterion on the thermodynamic properties and the surface morphology of the Gibbs adsorption layers. Indeed, most of the papers dealing with the G-LC and/or the LE-LC phase transitions in these monolayers involve nonionic surfactants [26][27][28][29][30][31][32]. It is, therefore, assumed that the ions show little or no effect on the properties of the monolayers of these nonionic surfactants.…”