Rheological properties and application of wormlike micelles formed by sodium oleate/benzyltrimethyl ammonium bromide

A pH-responsive anionic wormlike micellar (WLM) system formed by sodium oleate (NaOA) and benzyltrimethyl ammonium bromide were studied via rheological measurements and dynamic light scattering measurements. The anionic WLMs were used as templates to synthesize mesoporous silicas (MSs). The microstructures of the WLM system can be controlled by altering the pH. The transformation between NaOA and oleic acid changes the charges on the micelle surface and affects the viscoelasticity of the system. High NaOA concentration increases the activation energy (Ea) of the system, whereas a high pH value promotes the formation of spherical micelles and reduces the Ea of the solutions. By contrast, a low pH value increases the viscosity of the system given that the electrostatic repulsion between NaOA head-groups is weakened. However, if numerous NaOAs transform into insoluble oleic acids, the viscosity of the system will dramatically decrease. In addition, micelle length and NaOA concentration affect the microstructure of MSs. (C) 2016 Elsevier B.V. All rights reserved.