Abstract
Recently, in order to aim the improvement of properties of the conventional single-chained surfactants, novel surfactants with various structures containing gemini-type have been designed. Gemini surfactants are known to have high surface activities such as lower critical micelle concentration (CMC) and higher efficiency in lowering the surface tension than conventional surfactants, and show unique aggregation behavior, i.e., spontaneous vesicle formation at low concentration in solution. This review describes design and synthesis, surface–active properties such as CMC and ability in reducing the surface tension, and aggregation properties in aqueous solution for (1) heterogemini surfactants with nonidentical hydrophilic groups, hybridgemini surfactants with nonidentical hydrophobic groups, environmentally acceptable gemini surfactants containing amino acid or sugar in a molecule, (2) trimeric surfactants with three alkyl chains and three quaternary ammonium headgroups in a molecule, (3) supra-long chained surfactants with one alkyl chain of C18–C20 and two or three hydrophilic groups.
