The phase behavior of environment-friendly surfactants, polyoxyethylene phytosterylether (PhyEO
m) in water and water/polyoxyethylene dodecylether (C
12EO
4) systems was studied. In the PhyEO
10/water binary system, micellar solution (W
m), unidentified optically anisotropic liquid crystal (X) phase and lamellar (L
α) phases are formed successively with increasing surfactant concentration at room temperature. With hydrophilic PhyEO
20, the W
m, micellar cubic and hexagonal phases are formed in the binary system. With addition of C
12EO
4 to the dilute micellar solution of both PhyEO
m type surfactants, a highly viscoelastic solutions of worm-like micelles are formed. Addition of C
12EO
4 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 PhyEO
10/C
12EO
4/water system, the X-L
α phase transformation occurs via rectangular ribbon phase. The phase behavior of 5% PhyEO
m 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 PhyEO
m (m < 8) aqueous systems at all temperature. In the PhyEO
m 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 PhyEO
m (m = 17-20), the W
m phase of small aggregates exists in the entire temperature range.
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