Phase Equilibria in Systems of Water,Naphthenic Acids,and Phenols

A partial phase diagram has been determined for the system based on 5‐phenylvalerate, 4‐pentyphenol, and water at 25 °C. The system showed a very rich phase behavior in which many different isotropic solutions and liquid crystals were found. Both normal and reverse self‐assembly structures of the micellar and hexagonal types were noted. In the middle of the phase diagram, a lamellar liquid crystalline phase with a large swelling capacity was observed. When the aromatic alcohol was replaced by a long‐chain alcohol the reverse hexagonal structure disappeared. The effect of temperature and salinity on the phase behavior was also studied. Raising the temperature increased the micellar regions, while the lamellar phase was slightly reduced and the reverse hexagonal phase disappeared. Addition of salt gave the lamellar phase a smaller region of existence and the large extension towards the water apex disappeared. Introduction of an acid to the system resulted in a remarkable change of the phase behavior: both the normal micellar and lamellar regions were significantly reduced, while the reverse micellar region was significantly increased.