Cholesteryl poly oxyethylene ether

Uchegbu, I.F., et al. 1996. Phase-transitions in aqueous dispersions of the hexadecyl diglycerol ether (c(16)g(2)) non-ionic surfactant, cholesterol and cholesteryl poly-24-oxyethylene ether-vesicles, tubules, discomes and micelles. STP Pharm Sci 6 33. 

The lyotropic liquid crystals have been studied as a separate category of liquid crystals since they are mostly composed of amphiphilic molecules and water. The lyotropic liquid-crystal structures exhibit the characteristic phase sequence from normal micellar cubic (IJ to normal hexagonal (Hi), normal bicontinuous cubic (Vi), lamellar (1 ), reverse bicontinuous cubic (V2), reverse hexagonal (H2), and reverse micellar cubic (I2). These phase transitions can occur, for instance, when increasing the apolar volume fraction [9], or decreasing the polar volume fraction of the amphiphilic molecule, for example, poly(oxyethylene) chain length in nonionic poly(oxyethylene) alkyl (oleyl) or cholesteryl ether-based systems (10, 11). 

Furthermore, Kunieda and coworkers were interested in replacing the traditional surfactants with environmentally friendly molecules to overcome biodegradation processes and aquatic toxicity [25]. The main environmentally friendly surfactants that were explored were poly(oxyethylene) cholesteryl ethers (ChEOn, where n is the number of oxyethylene, EO, units) with a bulky hydrophobic cholesteric group of natural origin [25-27]. Due to the distinct segregation tendency between the hydrophilic and hydrophobic groups, compared to the conventional alkyl ethoxylated surfactants, their phase behavior as a function of ethylene oxide... 

Phase Transitions Within Poly(oxyethylene) Cholesteryl Ethers-Based Systems... 

In order to improve the understanding of these systems, Kunieda and coworkers examined the thermotropic behavior of poly(oxyethylene) cholesteryl ethers with different chain lengths, ChFOn, mixed with water at a fixed concentration ( 25 wt%) [32]. This study focused on the different fusion mechanisms that were involved in the solid-liquid phase transition. The soUd-Uquid transition temperature for ChFOn as a function of n is shown in Figure 4.3 (for comparison, the transition temperature for polyethylene glycol is also shown). In both cases, the transition temperature decreased when the chain length was diminished. However, for the cholesterol surfactant, when n < 10, a birefringent phase appeared between... 

It was shown that replacing the traditional surfactants by environmentally friendly molecules, such as poly(oxyethylene) cholesteryl ethers, to overcome the biodegradation process and aquatic toxicity resulted in the formation of diverse unique liquid-crystalline phases. The abihty to obtain novel intermediate phases was attributed to the bulky and nonflexible hydrophobic part of the surfactants and intricate hydrophobic-hydrophihc balance controlled by the different EO chain length. 

Kunieda s group reported numerous viscoelastic worm-like micellar systems in the salt-free condition when a lipophilic nonionic surfactant such as short hydrophilic chain poly(oxyethylene) alkyl ether, C EOni, or N-hydroxyethyl-N-methylaUcanolamide, NMEA-n, was added to the dilute micellar solution of hydrophilic cationic (dodecyltrimethylammonium bromide, DTAB and hexade-cyltrimethylammonium bromide, CTAB) [12-14], anionic (sodium dodecyl sulfate, SDS [15, 16], sodium dodecyl trioxyethylene sulfate, SDES [17], and Gemini-type [18]) or nonionic (sucrose alkanoates, C SE [9, 19], polyoxyethylene cholesteryl ethers, ChEO [10, 20], polyoxyethylene phytosterol, PhyEO [11, 21] and polyoxyethylene sorbitan monooleate, Tween-80 [22]) surfactants. The mechanism of formation of these worm-Hke stmctures and the resulting rheological behavior of micellar solutions is discussed in this section based in some actual published and unpublished results, but conclusions can qualitatively be extended to aU the systems studied by Kunieda s group. 

Sakai, T., and Kunieda, H. (2004) Phase behavior of poly (oxyethylene) cholesteryl ether/novel alkanolamide/ water systems. J. Colloid Interface Sci., 277, 235-242. 

Phase behavior and self-organized structures in water/ poly(oxyethylene) cholesteryl ether systems./. Phys. Chem. 5,108,12927-12939. 

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