Design of low-toxic and temperature-sensitive anionic microemulsions using short propyleneglycol alkyl ethers as cosurfactants.

The phase behavior of anionic microemulsions composed of water, sodium dodecyl sulfate (SDS), dodecane, and short propyleneglycol monoalkyl ethers (C(n)()PO(m)(); n = 3, m = 1 and n = 4, m = 2, 3) is studied. From the pseudoternary phase diagrams, it is inferred that C(n)()PO(m)() compounds have cosurfactant behaviors comparable to those of 1-butanol and 1-pentanol, which are the most efficient and widely used cosurfactants. In contrast to these alcohols, the C(n)()PO(m)() cosurfactants induce high temperature dependences in the SDS microemulsion systems. Furthermore, SDS/C(n)()PO(m)() microemulsions can be formed with small SDS concentrations (SDS/C(4)PO(3) mass ratio of 1/6.26). These have a low toxicity in contrast to systems containing genotoxic short ethyleneglycol ethers (C(n)()EO(m)()) as the cosurfactant. The strong temperature dependence can be favorable in the recovery of reaction products when the microemulsion is used either as a reaction medium or in extraction processes.