Synergistic Adsorption of MIBC/CTAB Mixture at the Air/Water Interface and Applicability of Gibbs Adsorption Equation

Abstract

The synergistic adsorption of a binary surfactant mixture was investigated by tensiometry and neutron reflectometry. The results directly contradicted the conventional Gibbs adsorption equation. The accompanied molecular simulation demonstrated a multilayer arrangement at the synergic conditions, with three distinctively oriented water layers. The positive synergism can be explained by considering the relationship between water orientation and surface tension, in a similar manner to Langmuir's proposal in 1920s. In spite of the supporting evidence, the relationship has not been quantified in literature. The molecular orientation and arrangement are not included in the current theoretical framework, which simplifies the adsorbed zone into a single monolayer. A new theoretical framework is needed to properly quantify the interfacial adsorption for the mixed surfactant systems.

Dynamic adsorption of a gemini surfactant at the air/water interface

“…16 The fitting results showed consistent agreement between modelled prediction and experiment at five concentrations. Moreover, the modelling was validated by using different initial guesses.…”

“…(1) in synergistic adsorption [16]. A critical comparison between six different variations [17] of the adsorption models, which are based on Eq.…”

Surfactant Interactions and Organization at the Gas–Water Interface (CTAB with Added Salt)

“…Besides that, most molecular modeling approaches to surfactant monolayer formation and resulting surface tension have applied to various lung surfactants and other lipid-based monolayer assemblies because of the biological relevance (e.g., refs − ). Martinez et al have examined via molecular modeling SDS monolayers, Phan et al have examined MIBC/CTAB mixtures, and Kong et al have examined simpler biosurfactants at different surface concentrations and have connected the findings to surface tension. The surface coverage dependency of surfactant aggregate morphologies at the interface has also received some molecular modeling attention for various surfactants (e.g., refs − ).…”

Dynamic Properties of Mixed Cationic/Nonionic Adsorbed Layers at the N-Hexane/Water Interface: Capillary Pressure Experiments Under Low Gravity Conditions

“…As model surfactants we have selected the cationic surfactant tetradecyl trimethyl ammonium bromide (TTAB) and the non-ionic surfactant tridecyl dimethyl phosphine oxide (C 13 DMPO), which are well studied at the interface between their aqueous solutions and air and various oil phases [2,3,[20][21][22] and references therein. Mixtures of these two surfactants have not been investigated yet, and also the number of adsorption studies for other surfactant mixtures at liquid interfaces are rather limited [23][24][25][26].…”