Structure of Aggregates in Diluted Aqueous Octyl Glucoside/Tetraethylene Glycol Monododecyl Ether Mixtures with Different Alkanols

摘要

A systematic study of the diluted lamellar phases of the OG/C_(12)E_4 system with different alkanols has been carried out by small-angle X-ray scattering (SAXS). The measurements have been made as a function of both the concentration and the alcohol type. Several different formfactormodels have been used to estimate the differences in bilayer topology induced by the presence of alcohol. For the infinite lamellae form factor (with a high-low-high electronic density profile across the membrane), there is a good fitting of samples with a X_(OG)= 0.1 ratios. Only the free parameters correspond to the pseudomolecule composition and hydration number, which resulted in two water molecules per ethylene oxide group in the polar head irrespective of the alkanol chain length and concentration. However, samples with higher OG content can be quite well fitted by a core-shell diskmodel. For the samples with higherOG content, we find the participation of OGin the disks to be important. From the line-shape analysis of SAXS data, the half-thickness of the hydrophobic layer and the thickness of the hydrophilic layer have also been obtained. The results suggest significant mixing of the surfactant acyl chains corresponding to both sides of the lamellae and the transition from vesicles to open bilayer fragments without macroscopic phase separation.