pH-switchable wormlike micelle formation by N-alkyl-N-methylpyrrolidinium bromide-based cationic surfactant

A non-covalent bonding method is utilized for forming pH-switchable wormlike micelles system by mixing N -hexadecyl- N -methylpyrrolidinium bromide-based cationic surfactant and pyrocatechol. The peculiarity of this system is that it has high viscoelasticity at acidic conditions and alkaline conditions, while it shows water-like behaviors at neutral conditions. Rheology, dynamic light scattering, and cryogenic-transmission electron microscopy results revealed that the microstructure transition between spherical micelles and wormlike micelles was the fundamental cause of the pH-switchable rheological properties. The unusual rheological and micellar responses of this system to pH are caused by different binding capacity of hydrotrope to C 16 MPBr as pH varies. Fluorescence analysis and nuclear magnetic resonance result support this hypothesis.