Novel sugar-based gemini surfactants: aggregation properties in aqueous solutiony

Gemini or dimeric surfactants can in principle be viewed as two conventional surfactants connected via a spacer at the level of the polar headgroups. A novel class of sugar-based gemini surfactants with rich and intriguing aggregation behavior in aqueous solution is the focus of this mini-review. The headgroup of the geminis consists of reduced sugars (glucose or mannose) connected to tertiary amines or amides. The alkyl tails have been varied in terms of tail length and degree of unsaturation. The spacers used are aliphatic [—(CH2)n—] spacers of varying length or short ethylene oxide (EO) spacers [—(CH2)2—(EO)2—]. By manipulating the molecular architecture and the solution conditions, a variety of supramolecular aggregates, such as vesicles and micelles, are formed from these sugar-based surfactants. In particular, the sugar-based gemini surfactants containing tertiary amines in the headgroup respond to the solution pH by forming vesicles in the monoprotonated state and micellar structures in the diprotonated (full protonation) state. The overall aggregation behavior is described well by conventional theories on surfactant aggregation, however, a surprising vesicle surface charge reversal as a function of pH will be described and discussed. Copyright # 2004 John Wiley & Sons, Ltd.