Influence of n-butanol on microemulsion system of sodium di-(2-ethylhexyl) succinic ester sulfonate

A new four component microemulsion system was obtained by adding n-butanol into a system of sodium di-(2-ethylhexyl) succinic ester sulfonate(AOT)/n-heptane/water.Phase diagrams of the AOT/n-butanol/n-heptane/water system that can exist stably at 25 ℃ were established and the results indicated that,the four component system can form wider O/W mono-phase microemulsion regions than AOT/n-heptane/water system.The four component microemulsion region was separated to two areas at a certain value R(molar ratio of water to AOT).Based on the measurement of the electrical conductance of the system,it was observed that during the dilution of the system with water,the microstructure of the system transforms subsequently from W/O to bi-continuous structure,rod liquid crystal,lamellar liquid crystal,bi-continuous structure and O/W.The structure parameters of the microemulsion were calculated and the results showed that,as the water content increases,free energy-△G0c→i of the both two microemulsion areas reduces and that is not advantageous to the stability of the system.The lower is the content of water;the more advantageous is for the formation and stability of the microemulsion system.The four component AOT/n-butanol/n-heptane/water system has a bigger microemulsion region than that of the AOT three component system,and is a suitable system for preparation of nano-particles.