Structure of vesicles in homogeneous short-chain polyoxyethylene cholesterol ether systems

Mixtures of the homogeneous nonionic surfactant trioxyethylene cholesterol ether, ChEO3 and water were examined by microscopy, small-angle X-ray scattering, differential scanning calorimetry, electron-spin resonance and fluorescence spectrometry. A lamellar liquid-crystalline phase with peculiar characteristics is found above 75% of surfactant concentration. This phase seems to consist of a rather rigid and ordered bilayer when compared with typical Lα-phases although the degree of crystallinity is less than that of Lβ-phases in nonionic systems with the same EO chain. The peculiarities of this phase are attributed to the rigid and bulky hydrophobic group of surfactant. The dispersion of this lamellar phase in water leads to the formation of very stable vesicles with a wide range of morphologies at rather low surfactant concentrations.