The stability boundaries of droplets of water/AOT/Dynol-604/isooctane mixed microemulsions

Abstract

In this study, we investigated the volumetric properties of water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate(AOT)/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/isooctane mixed microemulsions by density measurement at T = 303.15 K. It was observed that the volumetric interaction between the microemulsion droplets decreased with the increase of the content of Dynol-604 due to the reduction of electrostatic repulsion between the AOT head groups. The volumetric properties were analyzed by a proposed thermodynamic model to obtain the critical microemulsion concentrations and the maximum molar ratios ω _d,max of water to surfactants, which are the stable boundaries of the microemulsion droplets to accommodate the maximal content of water in their cores. It was found that ω _d,max increased from 62 to 77 as the mole fraction of Dynol-604 in mixed surfactants varied from 0 to 0.5. This result is further confirmed by conductivity measurements.

Graphical Abstract

Keywords:

• Density
• microemulsion
• volumetric property
• inter-droplet interaction
• stability boundary

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Projects 21373085).