The Phase Behavior Research Of Oleic Acid/N-Propanol/Water And Oleic Acid/DMF/bmimBF₄

Genarally,microemulsions are thermodynamically stable,isotropic,clear dispersions of oil,water,surfactant and cosurfactant mixtures,of which surfactant is once considered indispensable.However,Smith et al reported an W/O microemulsion composed of hexane,2-propanol and water,and this ternary system was considered as surfactant-free microemulsion(denoted as SFME)because no traditional surfactant involved in the system.So far,the understanding for SFMEs is very shallow.It is necessary to conduct systematic research to enhance scientific understanding of microemulsion and provide the basis for a wide range of applications.In this article,we employed ternary phase diagram and conductivity measurement,and systematically investigate phase behavior of the oleic acid/n-propanol/water and oleic acid/bmimBF4,bmimBF4 is greenhouse ionic liquid(IL),was used as aqueous phase in order to investigate the possibility of forming SFME and the type of SFME.The main conclusions is showed in below:1.There were a single-phase region and a two-phase region in ternary phase diagram for oleic acid/n-propanol/water and oleic acid/bmimBF4 systems,and single-phase region is microemulsion.Namely,the two systems are both surfactant-free microemulsion.2.For the system of oleic acid/n-propanol/water,a water-in-oleic acid(W/O)microemulsion,a bicontinuous(B.C.)microemulsion,a oleic acid-in-water(O/W)microemulsion were identified,which was confirmed by freeze-fracture transmission electron microscopy(FF-TEM)observations.But for the system of oleic acid/DMF/bmimBF4,a bmimBF4-in-oleic acid(IL/O)microemulsion,a oleic acid-in-bmimBF4(O/IL)microemulsion were identified.3.The studies on the electrical conductivity of SFME composed of oleic acid,Propanol,and water indicated that the conductance conduct of the reverse SFME is similar with conventional microemulsion.The system is in accordance with static percolation model.