2003 年 52 巻 8 号 p. 407-420
The phase behavior of potassium N-dodecanoyl-DL-alaninate (DL-KDA) and potassium N-dodecanoyl-L-alaninate (L-KDA) in water and water/decanol systems have been investigated. In the DL-KDA/water binary system, normal micellar solution (Wm), hexagonal (H1), bicontinuous cubic (V1) phase with Ia3d symmetry, and hydrated solid (S) phases are formed successively with increase in surfactant concentration at 25 °C. The phase behavior of L-KDA is essentially similar to that of the DL-KDA system except that the melting temperature of solid phase is high. In the DL-KDA/water/1-decanol system, lamellar (Lα), reverse hexagonal (H2) and reverse micellar (Om) phases are formed successively at 25 °C with increase in 1-decanol concentrations. Addition of decanol to the H1 phase induced a H1-Lα transformation via intermediate phases. At lower surfactant concentrations, nematic (N) and discotic lamellar (LαD) phases are found, whereas at higher surfactant concentrations rectangular ribbon (R1) and defected lamellar (LαH) phases are observed. The L-KDA/water/1-decanol system shows that a chiral nematic or cholesteric (Ch) phase is present (instead of the N phase observed in the DL-KDA system) at low decanol concentrations. However, a similar phase behavior is observed at high decanol concentrations for both surfactant systems. Hence, the optical activity of the surfactant has a significant effect on the phase behavior only in the presence of a low amount of decanol. This phenomenon has been explained by the change in the effective cross-sectional area at the aggregate interfaces.
