Liquid crystals in aqueous solutions of sodium naphthenates

The phase diagram of the sodium naphthenates (SN)/water system was determin ed between -5 and 95 degreesC. Oil, isotropic water solution, and birefring ent gel phases were observed. The appearance of the oil phase was caused by the hydrolysis of SN, After the system was allowed to stand for 3 weeks, a lamellar liquid crystal (LLC) phase separated from the rest of the system at 25 degreesC. This phase was always observed together with other phases. This phase behavior is attributed to different partition coefficient values of the individual constituents of sodium naphthenates between the phases. The partition coefficient difference also caused the appearance of a clear LLC and a turbid gel phase. Under the influence of agitation, the LLC phase with isotropic water solution transformed to giant vesicles; however the e quilibrium state of the LLC is of parallel stacked layer structure, Macrosc opic dislocations of the liquid crystal were observed, and they were anchor ed to the interface of the isotropic solution and the liquid crystal phases . These dislocations are similar to screw-type dislocations. The solubiliza tion curve of toluene by SN is analogous to that of hydrophobic materials b y a hydrotrope, (C) 2001 Academic Press.