Phase Diagrams and Microstructure of Ionic Microemulsion Systems Containing Various Monoalkyl Poly (oxyalkylene) Ethers

Abstract

Partial phase diagrams and microstructures were investigated in a one-phase microemulsion region of sodium oleate/monoalkyl poly (oxyalkylene) ethers/water ternary systems by conductivity, freezefracture electron microscopy and pulsed field gradient spin-echo (PGSE) NMR measurements. The influence of n-decane and glycerol trioleate on the ternary phase diagrams was also examined. Monomethyl, ethyl and butyl poly (oxyethylene) ethers and monobutyl ethers having both ethylene oxide (EO) and propylene oxide (PO) groups with different alkylene oxide chain length were used for this purpose. Although similar one phase microemulsion regions appeared in the monobutyl poly (oxyethylene) ether ternary systems, the microemulsion regions shrunk on increasing EO chain length by adding n-decane and glycerol trioleate. The introduction of PO groups at the terminal position of ethers had a spreading effect on the one phase region even in quaternary systems. Transition from water-in-oil to oil-in-water microemulsions through bicontinuous structures was found to occur with increase in water content.