Molecular structure-tuned stability and switchability of CO2-responsive oil-in-water emulsions

Hypothesis: Pseudo-Gemini surfactants (PGS) possessing switchable and recyclable features have drawn increasing attention on generating high-performance CO2-responsive emulsions for wide range and versatile applications. However, there is a lack of fundamental understanding on how the molecular structure of PGS affects the stability and switchability of emulsions. We hypothesize that the length and type of the spacer in PGS play a decisive role in controlling interfacial and switching properties. Experiments: Two series of PGS with different spacers were prepared through electrostatic association between amines and oleic acid. The interfacial activity and CO2-responsive properties of corresponding emulsions were systematically investigated by well-designed experiments and molecular dynamics simulations. Findings: Increasing the spacer length to allow the bent configuration leads to more tight arrangement of oleic molecules, consequently improving the interfacial activity. In addition, the introduction of amino group into the spacer dramatically promotes CO2 response of resulting PGS due to ehanced migration of the spacer from the interface to the aqueous phase after CO2 addition. These results are inspiring in designing controllable CO2-responsive emulsions for a wide range of industrial applications (e.g., enhanced oil recovery and oil-contaminated soil remediation). (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

This study investigates the impact of the molecular structure of pseudo-Gemini surfactants (PGS) on the stability and switchability of emulsions. The findings suggest that increasing the spacer length improves the interfacial activity, while introducing an amino group enhances the CO2 responsivity of PGS.