Self-Organizing Structures in Poly(oxyethylene) Oleyl Ether−Water System

Abstract

A phase diagram of a water−poly(oxyethylene) oleyl ether (POlE) system was constructed as a function of poly(oxyethylene) chain length at 25 °C. The POlEs contain a highly pure oleyl group, whose purity is above 99.7%. The POlEs are in a liquid state over a wide range of composition. The increase in the poly(oxyethylene) (EO) chain of POlE corresponds to the increase in the curvature of surfactant layer toward water or the increase in HLB (hydrophile−lipophile balance) number of the surfactant. Various self-organizing structures were found: hexagonal and lamellar lquid crystals, four kinds of isotropic liquid crystals, a sponge phase, and reverse hexagonal liquid crystal. The phase transition between normal hexagonal and lamellar liquid crystals were investigated at constant volume fraction of the oleyl group in system by means of small-angle X-ray scattering. Correlation among the phase behavior, the packing of oleyl chain in self-organizing structures, and the HLB of POlE is discussed. The effect of temperature on the phase behavior in the present system is also discussed.

Aqueous Phase Behavior of Ultra-Long Polyoxyethylene Surfactants

“…3, which is reproduced from previous data (8,13). With decreasing EO chain length or f value, micellar cubic phase (I 1 )-hexagonal (H 1 )-lamellar (L a )-reverse hexagonal (H 2 ) phase transition takes place.…”

“…Polyoxyethylene surfactants are widely used as emulsifying agents and detergents, and their aqueous phase behavior and self-organization have been extensively investigated (1)(2)(3)(4)(5)(6)(7)(8). With increasing the polyoxyethylene chain length, the surfactant layer curvature of self-assemblies in water changes from negative to positive.…”

Structure of Diglycerol Polyisostearate Nonionic Surfactant Micelles in Nonpolar Oil Hexadecane: A SAXS Study

“…Reverse micelles are mostly observed in the ternary mixtures of surfactant/water/oil, mostly in oil rich regions [11][12][13] . Furthermore, they have also been observed in aqueous systems of lipophilic surfactant in surfactant rich regions 14,15 . Only few reports exist that describes the formation of reverse micelles in organic solvents without water addition [16][17][18][19][20] .…”

Effect of Addition and Molecular Size of Triglyceride Oils on Phase Behavior and Surfactant Self-Assemblies

“…(1) (2) f L and f O are the volume fractions of lipophilic part of surfactant and oil in a system, respectively. v L is the volume of lipophilic part of surfactant molecule, which is obtained by a summation of methyl and methylene unit volume (7). n C is number of micelles in a unit cell of cubic phase.…”

“…Since spherical micelles have to maintain their structure at high surfactant concentration to form a discontinuous cubic phase, it is normally formed in aqueous surfactant systems with very hydrophilic nonionic surfactants, e.g. poly(oxyethylene)-type surfactant (7), poly(oxyethylene)-poly(oxypropylene)-poly (oxyethylene) triblock copolymer (8), polyglycerol ester (9), sucrose ester (10). However adding oil to a micellar phase or a hexagonal phase in an aqueous surfactant system often induces a formation of a discontinuous cubic phase (5,(11)(12)(13) since a structural transition of rod-like or elongated micelles to spherical micelles often takes place by the solubilization of oil (14).…”