On the Adsorption Kinetics of Surface-Chemically Pure n-Dodecanoic Acid at the Air/Water Interface

Abstract

The dynamic surface tension data for n-dodecanoic acid in 0.005 M hydrochloric acid, for as-received as well as for surface-chemically pure solutions, show the presence of a prolonged induction period, clearly indicating that the adsorption of this nonionic surfactant is not simply diffusion-controlled. A kinetic model for the reversible formation of monolayer islands, long known in the field of electrochemistry, is shown to also apply to the adsorption of n-dodecanoic acid at the air/water interface. The rate constant increases linearly with increasing bulk concentration, while the induction time decreases exponentially. The phenomenon of nucleation at the air/water interface is consistent with the direct experimental observation of the formation of solid-like patches as the interfacial region is drastically compressed.

Interpretation of surface-tension isotherms of n-alkanoic (fatty) acids by means of the van der Waals model

“…4) by the van der Waals model for n = 12 calls for additional discussion. At present, there is no direct experimental proof, but there are indirect evidences that a G-LE (gaseous-liquid expanded) twodimensional phase transition could exist for this acid [27]. As a rule, the G-LE transition occurs at very low surface pressure and low surface coverage [28], which makes difficult its detection by means of the Langmuir-trough method, especially for the lauric acid that exhibits solubility in the aqueous subphase.…”

Ellipsometric study of nonionic polymer solutions

“…Note that anomalous behavior of surface properties is frequently caused by traces of impurities of high surface activity. It is well known that their influence can be overwhelming in studies of adsorption kinetics [40][41][42][43][44]. Enormous efforts have been directed to elucidate the role of impurities and to minimize their effects.…”

Adsorption Kinetics of n-Nonyl-β-d-glucopyranoside at the Air−Water Interface Studied by Infrared Reflection Absorption Spectroscopy

“…The adsorption behavior of amphiphiles, which self-assemble at the air−water interface as Gibbs or Langmuir monolayers, is a subject of growing interest. − Kinetic, − thermodynamic, , and electric − methods have been applied to investigate the surface properties of amphiphilic molecules, and new sensitive surface spectroscopic techniques (X-ray and neutron reflectivity, linear and nonlinear optical techniques, − sum-frequency spectroscopy, and surface plasmon spectroscopy) have been developed. Insights into the microscopic and submicroscopic structures have been provided by Brewster angle microscopy (BAM), X-ray diffraction at gracing incidence (GIXD), Raman scattering, and infrared reflection absorption spectroscopy (IRRAS) …”