Solution Properties of Double-Chained Anionic Surfactants with Two Hydrophilic Groups and Two Hydrophobic Groups Having Different Alkyl Chains

Abstract

The solution properties of various double-chained anionic surfactants [disodium 5, 12-bis (2-alkyloxymethyl) -4, 7, 10, 13-tetraoxa-1, 16-hexadecanedisulfonate ; 2CnElS3, n=8, 10, 12, 14] with two anionic groups, differing in alkyl chain lengths, were examined by surface tension, micellar diameter, aggregation number and pNa measurements.Critical micelle concentration (cmc) and minimum surface tension at cmc (γcmc) decreased with an increase in alkyl chain length. At the same alkyl chain length, these parameters were less than those of anionic surfactants with single chains and single ionic groups. Micellar diameter (HD), aggregation number (N), occupied area of the hydrophilic group on the micellar surfaces (A) all showed maximum values at n=10. The degree of ionic dissociation of micelles (α) decreased with increasing alkyl chain lengths.Molecular packing on the micellar surfaces was found to depend on the steric structure of the bridge part in the surfactant molecule.