68207-00-1Relevant articles and documents
Switchable oil-water phase separation of ionic liquid-based microemulsions by CO2
Pei, Xiaoyan,Xiong, Dazhen,Pei, Yuanchao,Wang, Huiyong,Wang, Jianji
, p. 4236 - 4244 (2018/09/29)
Phase separation of microemulsions plays an important role in many applications such as oil recovery, nanomaterials synthesis, and chemical reactions. However, reversible switching from ionic liquid-based microemulsions to complete oil-water phase separation has not been reported so far. In this work, we developed a novel class of stimuli-responsive microemulsions composed of CO2-responsive ionic liquids, n-pentanol and water. The microstructures and phase behavior of the microemulsion systems before and after the bubbling of CO2 were investigated by electrical conductivity, dynamic light scattering, small-angle X-ray scattering, cryogenic transmission electron microscopy, and optical microscopy. It was found that these microemulsions could be reversibly switched from W/O monophase to complete oil-water phase separation upon alternate bubbling and removal of CO2 at atmospheric pressure. Furthermore, 13C NMR spectroscopy was used to understand the CO2-driven reversible phase separation of the microemulsions. The results suggest that the mechanism behind the reversible phase separation involved the reversible formation of bicarbonate and carbamate from the reaction between CO2 and the anions of the ionic liquids in the presence of water, which resulted in the increase of ionic strength (or vice versa) in the mixture. Using the microemulsions as microreactors, the phase separation protocol was applied in the Knoevenagel reaction for an efficient coupling of a chemical reaction, product separation, and recycling of the microemulsions.
Properties of Dilute Aqueous Solutions of Double-Chain Surfactants, Alkyldodecyldimethylammonium Bromides with a Change in the Length of the Alkyl Chains
Hiramatsu, Koichi,Kameyama, Keiichi,Ishiguro, Ryo,Mori, Masaki,Hayase, Hisao
, p. 1903 - 1910 (2007/10/03)
A series of cationic surfactants, dialkyldimethylammonium bromides with dodecyl as the primary alkyl chain and with methyl, ethyl, propyl, butyl, hexyl, octyl, and decyl as the second alkyl chain, as well as those with symmetric alkyl chains, dioctyl, didecyl and didodecyl ones, were synthesized, and their properties were investigated through measurements of the conductivity and air-liquid surface tension for their aqueous solutions to determine their critical micelle concentrations (cmc) and surface adsorption parameters in the formulation according to a two-dimensional lattice model in the form of the Frumkin equation. The change in cmc revealed that the free energy to transfer from water to the micelle per methylene unit is significantly small for asymmetric double-chain surfactants with a shorter second alkyl chain, and it approaches as elongating the second alkyl to those for the single-chain and symmetric double-chain surfactants. The free energy to transfer to an air-solution interface decreased approximately linearly with the total length of the hydrocarbon chains for all of the species examined. The lattice area for a symmetric double-chain surfactant molecule decreased with the length of its hydrocarbons. In a series of asymmetric ones, it showed a maximum for that with hexyl in its second alkyl.
