CO₂-Responsive Worm-like Micelle Based on Double-Tailed Surfactant

CO₂-responsive worm-like micelles (WLMs) are considered promising for applications in smart materials, enhanced oil recovery, and drug delivery because of their reversible and tunable properties. This study presents a novel system of CO₂-responsive WLMs, which is constructed using a double-tailed surfactant (DTS). When exposed to CO₂, the DTS molecules undergo protonation, resulting in the formation of ultra-long-chain cationic surfactants that self-assemble into worm-like micelles. The zero-shear viscosity of the DTS–CO₂ solution achieves approximately 300,000 mPa·s, which is 300,000 times higher than that of pure water. In contrast, the DTS–air solution exhibits a viscosity of only 2 mPa·s. The system retains a viscosity above 100,000 mPa·s across a temperature range of 25–120 °C under a CO₂ atmosphere. Moreover, it demonstrates reversible transitions between high- and low-viscosity states without any loss of responsiveness, even after multiple cycles. The critical overlap concentration of the DTS–CO₂ micellar system is determined to be 80 mM. This research offers valuable insights into the development of CO₂-responsive surfactants, highlighting their potential for designing advanced functional materials.