Levo vs. dextro. effect of the headgroup chirality on nanoassemblies

Surfactants that bear chiral headgroups form a variety of supra self-assembled nanostructures and can be used for different applications. In particular, ascorbic acid possesses two chiral centers, a rigid planar ring, a powerful redox active moiety, two acidic –OH residues, and a primary –OH group, and therefore is one of the most versatile polar headgroups for its peculiar properties. Here we report our studies on the nanoassemblies produced by L-(+)-ascorbyl-alkanoates (L-ASCn) and D-(-)-isoascorbyl-alkanoates (D-ASCn), carried out through DSC, SAXS, XRD, and surface tension experiments. The results suggest that the different configuration of the headgroups induces relevant changes in the structural and physico-chemical properties of the aggregates, due to the different hydration of the two epimers L-ascorbic and D-isoascorbic acid. The mixtures of D-ASC12 and L-ASC12 surfactants produce interesting phase diagrams, revealing the existence of a 1:1 compound, and of two eutectic points.