Solubility of ionic surfactants below their Krafft point in mixed micellar solutions: Phase diagrams for methyl ester sulfonates and nonionic cosurfactants

Many ionic surfactants with wide applications in personal-care and house-hold detergency show limited water solubility at lower temperatures (Krafft point). This drawback can be overcome by using mixed solutions, where the surfactant is incorporated micelles another surfactant, which soluble temperatures. The electrolytic conductivity for a binary mixture of anionic methyl ester sulfonates (MES) nonionic alkyl polyglucoside polyoxyethylene ether 5 °C during long-term storage were measured. Phase diagrams established; general theoretical model their explanation was developed checked experimentally. ternary phase studied mixtures include domains: micelles; + crystallites; crystallites, molecular solution. proposed methodology, utilizes equations thermodynamics minimum number experimental measurements, convenient construction such diagrams. results could increase range applicability MES–surfactants relatively high Krafft temperature, but various useful properties as excellent biodegradability skin compatibility; stability hard water; good wetting cleaning performance.