HELICAL AGGREGATION OF CHIRAL AMPHOTERIC SURFACTANTS CONTAINING HYDROXYL-GROUPS

An amphiphilic associated dimer compound containing both a hydroxy group and an asymmetric carbon atom exists in fibrous helical aggregates in an organic solution, when observed under an electron microscope. L-N-(2-Hydroxydodecyl)valine forms fibrous ggregates with a right-handed helicity, whilst those of the D-derivative have a left-handed twist. Chiral N-(2-hydroxydodecyl)tryptophan forms rod-like aggregates with no helicity. Further, as a similar example of the molecular dimer, N,N'-bis[1-carbonyl-D (or L)-12-hydroxyoctadecyl] alkanediamine ecyl] alkanediamine exhibits a fibrous twisted aggregate. Amphoteric surfactants (amino acid derivatives) containing a long alkyl group also have thermotropic liquid crystalline properties. Therefore, the -OH group in the 2-hydroxyalkyl chain plays an important role by enabling formation of an intermolecular hydrogen bond.