Unusual pH-responsive fluid based on a simple tertiary amine surfactant: the formation of vesicles and wormlike micelles†
A novel pH-responsive viscoelastic micellar system was prepared by N,N-dimethyl oleoaminde-propylamine without the addition of hydrotropes. The micellar system undergoes a gradual transition from vesicles to spherical micelles to wormlike micelles by adding an HCl solution. Rheology, Cryo-TEM and dynamic light scattering (DLS) results revealed that the pH-responsive flow behavior is attributed to the microstructural transition among the spherical micelles, vesicles and worm-like micelles. In this paper, we found out that a vesicle is extremely pH sensitive because the degree of protonation and the concentration of Cl− strongly affect the pH areas which could form worm-like micelles. The notable advantages of vesicles and worm-like micelles can be utilized to prepare pH-responsive viscoelastic fluids in the desired pH areas.