Structural and Macroscopic Characterization of a Gel Phase of Densely Packed Monodisperse, Unilamellar Vesicles

Abstract

In the phase diagram of the surfactant system sodium oleate/octanol/water a very stiff gel phase has been found, which is usually not present in similar systems. The phases of this system have been characterized by electric conductivity and rheological measurements. The structures present have been investigated by means of freeze-fracture electron microscopy and small-angle neutron scattering (SANS). These experiments have shown that addition of octanol to the surfactant solution for concentrations higher than 130 mM Na oleate leads to the formation of small unilamellar vesicles. For sufficiently high octanol content these vesicles are so monodisperse that they are able to form a densely packed system with long-range order and with a shear modulus that is about 100 times higher than normally found for vesicle systems. Upon dilution with water the vesicles swell while keeping the packing fraction constant until a maximum diameter of about 450 Å is reached, beyond which no further growth of the vesicles can take place. This is the first system of such type that forms a cubic-phase-like arrangement of monodisperse vesicles.

Spontaneous Vesicle Formation of an Industrial Single‐Chain Surfactant at Acidic pH and at Room‐Temperature

“…[6] Double-chain surfactants can be substituted by single-chain ones by adding a co-surfactant. [7][8][9][10][11][12] This leads also to spontaneous vesicle formation. For special applications particular single-tail surfactants were synthesised, and they can spontaneously form vesicles under certain conditions even without additive or co-surfactant.…”

“…For special applications particular single-tail surfactants were synthesised, and they can spontaneously form vesicles under certain conditions even without additive or co-surfactant. [12][13][14][15][16] Interestingly, all the surfactants mentioned in refs. [13][14][15][16][17] are cationic.…”

Investigations of vesicle gels by pulsed and modulated gradient NMR diffusion techniques

“…These systems are viscous and according to previous experimental investigations they consist of monodisperse unilamellar small vesicles with a radius of about 15-25 nm. [8][9][10][11] The fact that they are unilamellar and relatively small, is rather uncommon for spontaneously forming structures, i.e. their formation must be driven by the spontaneous curvature of the bilayer due to an asymmetry induced by the mixture of surfactant and cosurfactant.…”

“…5,[8][9][10] In this work the focus is on nuclear magnetic resonance (NMR). Here two diffusion NMR techniques are used to examine the structure, viz.…”

Supramolecular Self-organization of Potential Hydrogelators on Attracting Surfaces

“…Jørgensen et al report about hydrogelators which necessitate adding of ethanol or dimethylformamide [7]. Also mixtures with methanol [8] and other alcohols [9] or DMSO [10,11] etc. are common.…”