For microemulsions formulated using alcohols with the hydrocarbonate chain of medium length (i.e. 1-hexanol, 1-heptanol, 1-octanol), at a certain point (i.e. certain water concentration), the system viscosity has a sharp increase and a transparent, clear gel is formed. Can this be considered a microemulsion? Do you have any idea if it is birefringent or not? By any chance, are there articles on the subject of ternary phase diagrams for systems containing these alcohols as cosurfactants? Thank you.
There are lots of different systems like this that you can go to for literature. Lecithin, oil and water, as well phospholipids water and oil. Next it is an emulsion and may or may not be a gel depending on the classical definition you are using. The last part, is it birefringent is tough to know without know 1) what the surfactant is? 2) what is the mechanism of 'gelation'? and 3) are you below the Kraftt temperature. The kraftt temp is usually below the gelation temperature.
I'm using Tween 80 as a surfactant, so no Krafft temperature rule in this case. I'm working at 25 degrees Celsius. Being a clear, transparent system, it cannot be considered an emulsion. I consider as gel a system with no flow when in steady state, but with a small yield stress.
it is common for micro-emulsion formulation during pseudo ternary diagram preparation(oil to Smix ratio goes from 5: 5 to 2: 8) . liquid crystals are form in this region which form high viscous gels.
This article may be useful:
"Thermodynamics of Microemulsion Formation III. Enthalpies of Solution of Water in Chloroform as Well as Chloroform in Water Aided by Cationic, Anionic, and Nonionic Surfactants"
http://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCsQFjAB&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FSatya_Moulik%2Fpublication%2F14140029_Thermodynamics_of_Microemulsion_Formation%2Flinks%2F00b7d52b7e9c126ddf000000.pdf&ei=L6ztVMODOs69uATi_YDoCw&usg=AFQjCNGpDK1Kx5n5ZX3U6R5UWsEf8rKvRw&sig2=_2f9gvTG5J_hzUvCAj_RNA&bvm=bv.86956481,d.c2E
From classic point of view we can have several kinds of microemulsion oil/water, water/oil and the middle gel-like liquid crystal lamellar kind that contain elongated water and oil pools. So, it is common microemulsion, of course. See, please, Olsson U., Wennerstrom H. Adv. Colloid Interface Sci. 1994. Vol.49. P. 113. See also book Holmberg K., Jonsson B., Kronberg B., Lindman B. Surfactants and Polymers in Aqueous Solution. Second Edition 2003John Wiley & Sons, Ltd
In the case black oil is involved, the system is not transperant.
Hi Victor, a simple way to answer your question is to evaluate your system's stability. A true micro emulsion is thermodynamically stable because components are interacting on a molecular level (true dissolution). So, if your system is stable because there is no phase separation, you have a micro emulsion. In any case, the best giveaway that you are dealing with a micro emulsion is transparency.
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