A novel catanionic surfactant: Hexadecyltrimethylammonium dodecyl sulfate

The novel catanionic surfactant, hexadecyltrimethylammonium dodecyl sulfate, was prepared from the equimolar aqueous solutions of cationic, hexadecyltrimethylammonium bromide, and anionic, sodium dodecyl sulfate, surfactants. The composition, structure, morphology and thermal behavior of new compound were determined by chemical, X-ray diffraction, IR and 1H NMR spectra analyses, differential scanning calorimetry, thermogravimetry and polarizing microscopy. The thermal behavior of solid crystalline CTADS is rather complex because of its polymorphism, thermotropic mesomorphism and coexistence of ordered and disordered phases below the melting temperature. There are two parallel mechanisms during heating: structural transition of the system and transition from solid crystalline to liquid crystalline phase. Several polymorphic phases, all of the bilayered structure, were observed exhibiting a change of the basic lamellar thickness with temperature. Polarizing microscopy revealed a characteristic texture of the smectic phase.