Ribbon R, Phase

SAXS measurements of the Ql phase revealed five major peaks at 0.0583, 0.0923, 0.1099,0.1299, and 0.1451 A that have been translated into spacing ratios of V2 iVS /7. y/w Vl2 and were interpreted into a Pmin, P4ii2, or P4 43 space group of cubic symmetry. It was concluded that the ethanol mainly affected the polar region of the surfactant, since it was accommodated in the region of the headgroups. 

The water dilution line starting at 6 4 GMO/ water axis and crossing the bicontinuous cubic phase runs along the Ql phase and the sponge phase (L3) marked by a dashed line [28]. 

This unique phase was detected also by cryo-TEM, which provides direct structural symmetry information. The cryo-TEM image of the Ql sample exhibited highly ordered domains with cubic symmetry (arrows in the image) and was further confirmed by the fast Fourier transformations (EFT) (Eigure 4.10 [28]). The FFT transformations were fitted to the bcc or fee lattices, with points a, h, and c in the figure indexed as (2 0 0), (1 1 0), and (2 2 0) for the bcc structure, or (2 2 0), (0 2 0), and (0 4 0) for the fee phase. The lattice parameter was found to be 103 2A. 

It was concluded that the incorporated ethanol, as a third component, shongly affected the Hpid headgroups, causing a moderate effect on the lateral forces acting within the polar and apolar regions of the membrane, bending the layers and enabling the formation of cubic phase with very low viscosity. 

In a further study, the authors demonstrated that the Ql phase can solubilize high concentrations of the water-insoluble anti-inflammatory drug sodium diclofenac (Na-DFC) [40]. Up to 0.4 wt% Na-DFC, the Ql structure remained intact 

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