4. pH-Responsive Wormlike Micelles

pH has been known for a long time and frequently used as a facile, inexpensive trigger to control molecular assemblies and thereby the bulk properties of the corresponding solutions. pH-responsive WLMs have been developed not only based on commercially available surfactants in the presence of hydrotropes, but also through the design of surfactant mixture composition and surfactant architecture. This chapter introduces pH-responsive wormlike micellar systems fabricated through the introduction of hydrotropes to conventional surfactant-based wormlike micellar systems, in appropriate mixtures of surfactants, or by modifying the surfactant molecular architecture with pH-sensitive functional groups, either the hydrophilic head or the hydrophobic tail. It is worth pointing out that a disadvantage of this trigger is that the cyclic addition of acid and base may deteriorate the repeated use of the wormlike micellar systems.