Symmetrical catanionic surfactants

Symmetrical catanionic surfactants consist of anionic and cationic surfactants of the same chain length. Alkylammonium alkyl sulfates [such as decylammonium decyl sulfate (DeADeS), dodecylammonium dodecyl sulfate (DDADDS), and tetradecylammonium tetradecyl sulfate (TDATDS)] are prepared by mixing equimolar solutions of alkylammonium chloride and the corresponding alkyl sulfate. The reaction can be represented as... [Pg.460]

The symmetrical catanionic surfactants exhibit complex thermal behavior characterized by several successive phase transitions. Three endothermic transitions are displayed by heating the solid crystalline-solid crystalline, the solid crystalline-liquid crystalline, and the liquid crystalline-isotropic liquid phase. On cooling, all compounds reversibly undergo the isotropic liquid-liquid crystalline transition, while other transitions exhibit peculiar properties. There is no... [Pg.460]

Additionally, X-ray diffraction patterns of hexadecyltrimethylammonium alkyl sulfates in the heating cycle display a superposition of rather sharp diffraction lines on diffuse amorphous maxima, indicating the presence of two phases. One phase is the three-dimensionally ordered crystalline phase, and the other is a disordered one, indicating some kind of a two-dimensionally ordered liquid crystalline phase. The presence of a disordered phase in addition to the ordered phase is not observed in the symmetrical catanionic surfactants [62]. [Pg.470]