Formulating Middle Phase Microemulsions Using Extended Anionic Surfactant Combined with Cationic Hydrotrope

Abstract

The phase behavior of systems containing sodium alkyl polypropylene oxide sulfate with equimolar ratio of polypropylene oxide ammonium chloride was determined as a function of salt concentration and alkane carbon number at ambient temperature. Visual inspection as well as cross polarizers were used to detect anisotropy. Solubilization ratios for oil and brine in the middle phases were measured and used to calculate the interfacial tension (IFT) between the microemulsion and oil or brine. The fish diagram is presented showing a minimum amount of 0.20 wt% surfactant needed to form the middle phase. Swelling increases with decreasing the alkane carbon number of the oil. Ultra low IFT values were predicted for the systems investigated.

Keywords:

• Cationic hydrotrope
• extended surfactant
• microemulsion
• middle phase

Acknowledgments

The authors would like to thank Paul Filler, Sasol North America, Inc., and Paola Pastorelli, Sasol Italy, for kindly providing us with the extended surfactant samples and Peter Schwab, Evonic Goldschmidt, Germany, for kindly providing us with the Variquat samples. This work was supported by the Swedish Research Council.