Identification of transitions in lyotropic mesophases in hexaethylene glycol dodecyl ether–water by precision densimetry

Abstract

The temperature dependence of the density has been measured for several concentrations of the hexaethylene glycol dodecyl ether (C₁₂E₆)–water (H₂O) system, which exhibited lyotropic mesophases. The transitions from the lamellar (L_α) phase to the micellar solution (L₁) phase and from the hexagonal (H₁) phase to the micellar solution phase are of first order, and the molecular packing in the L_α phase is closer than that in the H₁ phase. The mixture with 65.0 wt.% C₁₂E₆ exhibits L₁, cubic (V₁), H₁ and L_α phases. The individual phase transitions between the H₁, V₁, L_α and L₁, phases in sequence were clearly evident in the reduced density. The H₁–V₁ and V₁–L_α phase transitions are of second order.