Abstract
The phase behavior of environment-friendly surfactants, polyoxyethylene phytosterylether (PhyEOm) in water and water/polyoxyethylene dodecylether (C12EO4) systems was studied. In the PhyEO10/water binary system, micellar solution (Wm), unidentified optically anisotropic liquid crystal (X) phase and lamellar (L α) phases are formed successively with increasing surfactant concentration at room temperature. With hydrophilic PhyEO20, the Wm, micellar cubic and hexagonal phases are formed in the binary system. With addition of C12EO4 to the dilute micellar solution of both PhyEOm type surfactants, a highly viscoelastic solutions of worm-like micelles are formed. Addition of C12EO4 to the liquid crystalline phases formed in binary system results in the formation of the L α phase, which extends over wide concentration range. In the PhyEO10/C12EO4/water system, the X-Lα phase transformation occurs via rectangular ribbon phase. The phase behavior of 5% PhyEOm with various EO-chain length, ranging from m = 5 to 20 was studied in a wide range of temperature (20°-100 °C). A phase separation occurs in the lipophilic PhyEOm (m < 8) aqueous systems at all temperature. In the PhyEOm with intermediate EO-chain length (11 < m < 16), small micelles undergo enormous one-dimensional growth upon increasing the temperature and form viscoelastic solution, followed by a phase separation; whereas in the long EO-chain PhyEOm (m = 17-20), the Wm phase of small aggregates exists in the entire temperature range.
