Multifunctional pH‐Responsive Gemini Surfactant

Abstract

Stimuli‐responsive surfactants have garnered significant attention as promising candidates for diverse applications in efficient oil recovery, programmable all‐liquid devices, and microreactors owing to their dynamic interfacial self‐assembly behavior under specific triggers. However, contemporary applications of stimuli‐responsive surfactants remain constrained within monofunctional paradigms, significantly impeding their integration into advanced multifunctional manufacturing. Here, an interesting pH‐responsive gemini surfactant is reported that can dynamically switch between gemini (GTL, pH ≥ 8.0) and single‐chain (TL+, pH ≤ 6.0) conformation, facilitating adaptive functionalities spanning reversible oil/water separation, structured liquid, 3D printing, and thermal insulative aerogels. As triggered by CO2/Ar, GTL acts as a smart emulsifier, achieving efficient oil/water separation over 10‐cycle reusability. The electrostatic co‐assembly of TL+ and sulfated cellulose nanocrystals (CNC‐OSO3−) at the oil‐water interface drives a jammed film, yielding a reconfigurable all‐liquid structure. Furthermore, TL+/CNC‐OSO3−‐stabilized emulsions exhibit self‐supporting properties, enabling dual functionality as 3D‐printable inks for complex patterning in air/oil baths, and as advanced precursors for thermal insulative aerogels. Density functional theory calculations reveal the pH‐dependent adsorption of GTL at the oil‐water interface and the co‐assembly of TL+/CNC‐OSO3− driven by abundant non‐covalent interactions. This pH‐responsive surfactant addresses the critical demand for multifunctional manufacturing, establishing an adaptive paradigm for next‐generation smart materials.