Block Copolymer Micelle Shuttles with Tunable Transfer Temperatures between Ionic Liquids and Aqueous Solutions

Abstract

Four poly((1,2-butadiene)- block-ethylene oxide) (PB-PEO) diblock copolymers were shown to self-assemble into micelles with PB cores and PEO coronas (including spheres, cylinders, and vesicles) in the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). All four systems exhibited the "micelle shuttle" (He, Y.; Lodge, T. P. J. Am. Chem. Soc. 2006, 128, 12666-12667), whereby PB-PEO micelles transferred, reversibly and with preservation of micelle structure, from an aqueous phase at room temperature to a hydrophobic ionic liquid at high temperature. The micelle size (both mean and distribution) depends on whether it was initially dissolved in water or in the ionic liquid, but the initial micelle structures in the ionic liquid were shown by dynamic light scattering to be preserved during the transfer and persist essentially unchanged for months in both the ionic liquid and water. The transfer was shown to be driven by the deteriorating solvent quality of water for PEO at high temperature, while the ionic liquid remains a good solvent. The transfer temperature could be tuned by adding ionic or nonionic additives to the aqueous phase to change the solvent quality of water for PEO, and by using ionic liquids with different polarity.

Room temperature ionic liquids as emerging solvents for the pretreatment of lignocellulosic biomass

“…Another option is the use of anion exchange resins for isolation of the ionic liquid as a salt (Bonhote et al, 1996), which could be accompanied by at least partial precipitation of the lignin. Moreover, if the newly formed ionic liquid is hydrophobic (e.g., [BMIM]PF 6 ), one may envision the use of a temperaturecontrolled, micellization-transfer-demicellization ''shuttle'' between the ionic liquid and an aqueous phase using poly(ethylene oxide)-containing (PEO) block copolymers, as described by Lodge and coworkers (Bai et al, 2008). For lignin extraction, micelles formed from a block copolymer containing a lignin-compatible block and a PEO block could serve as nanocarriers for the lignin, which could be transferred from the ionic liquid to an aqueous phase upon contact due to the preferential affinity of the micelles for water in a certain temperature range.…”

Structural effects of polyethers and ionic liquids in their binary mixtures on lower critical solution temperature liquid-liquid phase separation

“…51,52 Block copolymers containing PEO segments and IL-incompatible segments, which form micelles in ILs, have been studied and successfully utilized for micellar shuttles at the IL/water interfaces and in thermoreversible ion-gel formation. [53][54][55][56][57][58] As shown in Table 3, polyethers other than PEO, such as PGME, PEEGE, PEGE and PPO, exhibit LCST phase separation in these ILs. This result is very important, because PPO and its block copolymers are commercially available and we can systematically examine these LCST behaviors.…”

Stimuli‐triggered phase transfer of polymer‐inorganic hybrid hairy particles between two immiscible liquid phases

“…Because of these unique features, room temperature ILs are being intensively investigated as media for reactions and separation . Lodge and coworkers reported a series of poly(ethylene oxide) (PEO)‐based block copolymer micelle and vesicle shuttles that can transfer back and forth between water and hydrophobic ILs in response to temperature changes . The micelles and vesicles with PEO coronas resided preferentially in water at room temperature, moved across the interface to the IL phase at elevated temperatures, and transferred back to the aqueous phase upon cooling.…”