Advances in heterogemini surfactants

Symmetrical gemini surfactants are made up of two identical amphiphilic moieties covalently connected at the level of the headgroups by a spacer chain. The gemini surfactants have been attracting increasing attention owing to their novel and complicated self-assembly behaviour. Up to now, however, only a few works have been focused on unsymmetrical gemini surfactants (also called heterogeminis) because of the difficulty for synthesis. The initial investigations showed that the heterogeminis have more molecular structure factors that can be regulated and governed during the process of the molecular self-assembly than symmetrical geminis. Some novel results had been obtained, for example, enhanced driving force of enthalpy factor, constructed counterions-free systems by the heterogeminis containing cationic-anionic head groups and bound vesicles formed by heterogeminis making use of its different length of alkyl chains, etc. The advances in investigating heterogemini surfactants are reviewed and the potential significance in study of heterogeminis is pointed out.