Nature-like synthetic alkyl branched-chain glycolipids: a review on chemical structure and self-assembly properties

This review presents the structure/property relationship of two classes of synthetic branched-chain glycolipids, namely the Guerbet and isoprenoid glycosides, in particular highlighting the importance of chain branching to their self-assembly properties. Alkyl chain branching in glycolipids tends to stabilise the reversed type phases as well as a lamellar (L-alpha) phase. These glycolipids exhibit several reversed bicontinuous cubic phases (Q(II)), the reversed hexagonal phase (H-II) and the lamellar phase. The detailed structures of the Q(II) phases are governed by the balance between the hydrophobic chain bulkiness and the headgroup interaction, including hydrogen bonding. Among the isoprenoid glycolipids, an aqueous isoprenoid xyloside exhibits a bicontinuous cubic phase with a diamond Q(II)(D) (Pn3m) space group at full hydration and that of a glucoside adopts the stable reversed micellar cubic phase of an Fd3m space group. In the series of Guerbet glycolipids, the ones with longer chains may form stable bicontinuous cubic phases (diamond and Schwarz primitive) in dry condition, as well as the gyroid Q(II)(G) (Ia3d) in excess water. The phase behaviours of these synthetic glycolipids are comparable to those observed in other natural glycolipids, thus making them potentially useful for applications in both nano-electronics and biomedicine, as therapeutic delivery systems.