Adsorption Layer of Potassium Dodecanoate and Diglycerol Derivative Mixtures at the Air/Water Interface Studied by Neutron Reflectivity and Small-Angle Neutron Scattering.

Authors

Miki Abe, Hiromi Miki, Akari Habuka, Takeshi Yamada, Ryosuke Toyoshima, Shiho Yada, Koichi Mayumi, Tomokazu Yoshimura, Norifumi L Yamada

Published in

Langmuir : the ACS journal of surfaces and colloids. Jul 27, 2026. Epub Jul 27, 2026.

Abstract

The behavior of the air/water interface in a one-component surfactant system is studied by performing surface tension measurements and analysis based on Gibbs adsorption isotherms. However, this method is inefficient for evaluating the surface composition of surfactant-additive systems, which is important for optimizing the composition of industrial products according to their practical applications. In this study, the diglycerol derivative 2GlyPO₉ with polyoxypropylene chains, developed for industrial applications, was investigated to gain insight into how its mixing with potassium dodecanoate (C₁₁COOK) improves the foam stability. The adsorption properties at the air/water interface were examined by conducting surface tension and neutron reflectivity measurements, and the aggregation structure was studied using small-angle neutron scattering. With increasing C₁₁COOK concentration, the surface tension decreased through the following processes: (1) both 2GlyPO₉ and C₁₁COOK were adsorbed, (2) 2GlyPO₉ was replaced with C₁₁COOK at the interface, (3) 2GlyPO₉-based aggregates were formed in solution, and (4) mixed micelles were formed with C₁₁COOK. This process changed slightly depending on the solution used. At excessive 2GlyPO₉ concentrations, process (2) was less likely to occur than at lower concentrations because 2GlyPO₉ formed aggregates, even in the absence of C₁₁COOK. When C₁₁COOK was mixed with another diglycerol derivative, 2GlyEO₉, in which the hydrophobic polyoxypropylene chains of 2GlyPO₉ were replaced with hydrophilic polyoxyethylene chains, process (3) was skipped because no aggregates of 2GlyEO₉ were formed. Compared with the C₁₁COOK solutions without diglycerol derivatives, the addition of 2GlyPO₉ lowered the surface tension above the critical micelle concentration, whereas 2GlyEO₉ did not produce this effect, although the surface excess concentration of C₁₁COOK decreased in both cases. This detailed structural analysis conducted at the interface and in solution using neutrons provides useful insights into the mechanism of adsorption at the air/water interface, particularly in surfactant-additive systems.

PMID:
42504517
Bibliographic data and abstract were imported from PubMed on 27 Jul 2026.

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