PHYSICAL SCIENCE OF THE DIOCTADECYLDIMETHYLAMMONIUM CHLORIDE WATER-SYSTEM .1. EQUILIBRIUM PHASE-BEHAVIOR

The equilibrium phase diagram of the dioctadecyldimethylammonium chloride (DODMAC)-water system was determined below 80°C, and concentrated regions were investigated to 150°C. Two equilibrium polymorphic forms of the dry crystal and two equilibrium crystal hydrates (a mono- and a dihydrate) were found. (A metastable dihydrate was also prepared.) The only liquid crystal phase which exists is the lamellar phase; its composition ranges from about 31.5% DODMAC to as high as 95%, depending on temperature. The Krafft discontinuity lies at 47.5°C. The "coagel" and "gel" states, previously reported within concentrated regions of this system, were shown to consist of the mono- and dihydrate crystals, respectively. Slow phase reactions and the formation of stable colloidal structure in biphasic regions severely hampered this study. © 1990 American Chemical Society.