The catanionic system dodecyltrimethylammonium hydroxide-n-dodecanephosphonic acid-water. Triangular phase diagram

The triangular phase diagram of the system dodecyltrimethylammonium hydroxide (DTAOH)-dodecanephosphonic acid (H2DP)-water was studied by several techniques. The DTAOH-rich zone could not be studied because DTAOH decomposed when it was dried. Pure H2DP only forms lamellar mesophases with water. The inclusion of DTAOH in the system produces the appearance of cubic and hexagonal mesophases. The gradual increase in DTAOH proportion lead to the gradual reduction in the existence of the lamellar mesophase domain, and increase of the hexagonal liquid crystal domain. At high DTAOH content, the lamellar mesophase disappeared. This behavior was explained by the gradual destruction of the hydrogen-bonded structure in the polar headgroup layer of liquid crystal aggregates. H2DP-rich anhydrous crystals were triclinic.