Small-angle X-ray scattering study on nano-scale structures controlled by water content in a binary water/ionic liquid system

摘要

We report the water-in-ionic-liquid microemulsions (ME) formed in a binary water/ionic liquid system, without organic solvents, using a surfactant ionic liquid (SAIL) based on 1-butyl-3-methylimidazolium (C(4)mIm(+)) as the cation and dioctyl sulfosuccinate (AOT(-)) as the anion. Small-angle X-ray scattering (SAXS) revealed that MEs were stably formed in the binary water/SAIL solutions in the low water content region (water volume fraction, phi(w) 0.1), and the ME size systematically increased with increasing phi(w). We further investigated the nanostructures of the high phi(w) region using a combination of SAXS and rheological measurements and found that the MEs changed to a stacked lamellar structure comprising SAIL bilayers and water phases at phi(w) 0.12. At the largest water content, phi(w) = 0.99, vesicle structures were obtained.