Formation of Diverse Mesophases Templated by a Diprotic Anionic Surfactant

Abstract

The synthesis system for mesophase formation, using the diprotic anionic surfactant N-myristoyl-L-glutamic acid (C(14)GluA) as the structure-directing agent (SDA) and N-trimethoxylsilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) as the co-structure-directing agent (CSDA), has been investigated and a full-scaled synthesis-field diagram is presented. In this system we have obtained mesophases including three-dimensional (3D) micellar cubic Fm3m, Pm3n, Fd3m, micellar tetragonal P4(2)/mnm, two-dimensional (2D) hexagonal p6mm and bicontinuous cubic Pn3m, by varying the C(14)GluA/NaOH/TMAPS composition ratios. From the diagram it can be concluded that the mesophase formation is affected to a high degree by the organic/inorganic-interface curvature and the mesocage-mesocage electrostatic interaction. Bicontinuous cubic and 2D-hexagonal phases were found in the low organic/inorganic-interface curvature zones, whereas micellar cubic and tetragonal mesophases were found in the high organic/inorganic-interface curvature zones. Formation of cubic Fm3m and tetragonal P4(2)/mnm was favoured in highly alkaline zones with strong mesocage-mesocage interactions, and formation of cubic Pm3n and Fd3m was favoured with moderate mesocage-mesocage interactions in the less alkaline zones of the diagram.