A NOVEL CATANIONIC SURFACTANT - HEXADECYLTRIMETHYLAMMONIUM DODECYL-SULFATE

The novel catanionic surfactant, hexadecyltrimethylammonium dodecyl su lfate. was prepared from the equimolar aqueous solutions of cationic, hexadecyltrimethylammonium bromide, and anionic, sodium doedecyl sulfa te, surfactants. The composition, structure, morphology and thermal be havior of new compound were determined by chemical, X-ray diffraction, IR and H-1 NMR spectra analyses, differential scanning calorimetry, t hermogravimetry and polarizing microscopy. The thermal behavior of sol id crystalline CTADS is rather complex because of its polymorphism, th ermotropic mesomorphism and coexistence of ordered and disordered phas es below the melting temperature. There are two parallel mechanisms du ring heating: structural transition of the system and transition From solid crystalline to liquid crystalline phase. Several polymorphic pha ses, all of the bilayered structure, were observed exhibiting a change of the basic lamellar thickness with temperature. Polarizing microsco py revealed a characteristic texture of the smectic phase.