A pseudo-quantitative ternary surfactant ion mixing plane phase diagram for a cationic hydroxyethyl cellulose with dodecyl sulfate counterion complex salt

Abstract

The surfactant ion mixing plane phase diagram was constructed for cationic hydroxyethyl cellulose dodecyl sulfate (cat-HECDS), sodium dodecyl sulfate (NaDS) and water. The number of phases and structures present in the prepared ternary composition were assessed visually and guided the placement of phase boundaries. Two multi-phase regions surround a large, central one-phase isotropic region. In the dilute portion of the diagram, an isotropic-isotropic two-phase region exists along the water-complex salt axis. A concentrated multi-phase region adjacent to the water-NaDS axis includes a three-phase region defined as isotropic-hexagonal-monoclinic surrounded by three two-phase regions of isotropic-monoclinic, isotropic-hexagonal, and hexagonal-monoclinic.This phase diagram is similar to one previously published in this journal [Svensson et al., Colloids Surf. A, 228 (2003) 91–106]. Here the degree of cationic substitution on the polymer was reduced by half. This resulted in a shift in the locations of the phase boundaries, but not the phases and structures, present in this plane. Evaluating the phase boundaries as a function of anion:cation molar ratio highlighted the impact of the hydrophobic binding of excess surfactant monomers to the polycation-surfactant anion network on the phase transitions in the surfactant ion mixing plane phase diagrams for cat-HECDS.