Multifunctional pH-Responsive Gemini Surfactant

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 CO 2 /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-OSO 3 − ) at the oil-water interface drives a jammed film, yielding a reconfigurable all-liquid structure. Furthermore, TL + /CNC-OSO 3 − -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-OSO 3 − 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.