Studies on the synthesis, surface activity and the ability to form pH-regulated wormlike micelles with surfactant containing carboxyl group

In this article, a series of pH regulated surfactants with different hydrophobic chain length and carboxyl group molecular structure positions were designed and synthesized. The molecular structure of pH regulated surfactants was analyzed by mass spectrometry and 1H NMR spectroscopy. The results of the surface activity test show that the pH regulated surfactants have lower surface tension, which indicates that it is easier to adsorb directionally at the gas-liquid interface and to aggregate in solution. Both inorganic and organic counterions can improve the viscosity of the system to some extent, but the viscosity-increasing ability of organic counterions is much higher than that of inorganic counterions. The results of rheology and dynamic light scattering show the transition from spherical micelles to wormlike micelles was observed when pH increased from 5 to 8 in the Docos-13-enoylamino-acetic acid (Gly-22)/Trimethylstearylammonium chioride (ODAC) system. The results of Cryo-transmission electron microscopy verify this result directly. Also, the experimental results show that the Gly-22/ODAC system has excellent pH cycle regulation performance, which can significantly reduce the application cost of the system.