Model-Free Analysis of Critical Micellar Concentrations for Detecting Demixing in Surfactant Mixtures

Abstract

Aqueous mixtures of two or more surfactants are often employed for research or industrial purposes because such mixtures offer advantages over single-surfactant systems. This is particularly true for mixtures of fluorocarbon (FC) and hydrocarbon (HC) surfactants, which display a broad range of mutual miscibilities in mixed micelles. Unfortunately, the prediction and even the experimental elucidation of the micellar mixing behavior of surfactant mixtures remain challenging, as evidenced by conflicting results and conclusions derived from diverse, and often complex, mixing models. One of the most intriguing questions is whether certain combinations of FC and HC surfactants form only one type of mixed micelle or rather demix into two micelle populations, namely, FC-rich and HC-rich ones. Here, we demonstrate a novel approach to the model-free analysis of critical micellar concentrations (CMCs) of surfactant mixtures that is based on a fit of the experimental data with cubic splines using a stringent thermodynamic criterion for mixing. As a proof of principle, we analyze CMC values determined by isothermal titration calorimetry and confirm the conclusions with the aid of combined H- andF-NMR spectroscopy. Specifically, we show that aqueous mixtures of an FC maltoside and an HC maltoside conform with the assumption of only one type of micelle regardless of the mixing ratio, whereas combining the same FC surfactant with an HC surfactant carrying a zwitterionic phosphocholine headgroup gives rise to two coexisting micelle populations at high mole fractions of the FC maltoside.

Solution Properties of Alkyl β‐D‐Maltosides

“…However, there are not enough data and messages available to support effectively the application in the field of life and material sciences although there are some available features/parameters including critical micelle concentration (CMC) (Frotscher et al, 2017;Matsuoka et al, 2017;Santonicola et al, 2008), sugar headgroup structure (Ehsan et al, 2016), field-induced phase transition (Hashim et al, 2017), paracellular permeation (Gradauer et al, 2017), and cell metabolism (Smułek et al, 2017). The corresponding fairly accurate and feasible screening should rely heavily on the empirical evidence, exhaustive trial-and-error process and rational thinking, and even intuitive approach.…”

Erlotinib-Guided Self-Assembled Trifunctional Click Nanotheranostics for Distinguishing Druggable Mutations and Synergistic Therapy of Nonsmall Cell Lung Cancer

“…Various reports have demonstrated that amphiphilic Cs derivatives modified with the hydrophobic moieties can self-assemble into micelles. , CE7 composed of hydrophilic Cs chains and hydrophobic erlotinib and Cy7 groups can undergo self-assembling to form nanoparticles in an aqueous solution. CMC is the threshold concentration at or above which the self-assembly happens . A simple fluorescence method was used to determine the CMC of CE7 to prove the self-assembly of CE7.…”

“…CMC is the threshold concentration at or above which the selfassembly happens. 27 A simple fluorescence method was used to determine the CMC of CE7 to prove the self-assembly of CE7. To avoid the interference of the fluorescence of Cy7, FITC (λ ex /λ em = 490/519 nm) was chosen as a fluorescence probe.…”

Self‐Assembly of Protein‐Containing Lipid‐Bilayer Nanodiscs from Small‐Molecule Amphiphiles

“…19 F-NMR has been applied to fluorinated surfactants in order to monitor micellization [13,7] or mixing with conventional hydrocarbon surfactants [24][25][26] and lipids. [13] Similarly, we used 19 F-NMR to monitor the change in the environment of the terminal CF 3 group of F 6 ODG throughout the solubilization process.…”