Self-Assembly of Block Copolymer Micelles in an Ionic Liquid

Abstract

Four amphiphilic poly((1,2-butadiene)-block-ethylene oxide) (PB-PEO) diblock copolymers were shown to aggregate strongly and form micelles in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]). The universal micellar structures (spherical micelle, wormlike micelle, and bilayered vesicle) were all accessed by varying the length of the corona block while holding the core block constant. The nanostructures of the PB-PEO micelles formed in an ionic liquid were directly visualized by cryogenic transmission electron microscopy (cryo-TEM). Detailed micelle structural information was extracted from both cryo-TEM and dynamic light scattering measurements, with excellent agreement between the two techniques. Compared to aqueous solutions of the same copolymers, [BMIM][PF(6)] solutions exhibit some distinct features, such as temperature-independent micellar morphologies between 25 and 100 degrees C. As in aqueous solutions, significant nonergodicity effects were also observed. This work demonstrates the flexibility of amphiphilic block copolymers for controlling nanostructure in an ionic liquid, with potential applications in many arenas.

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.…”

The effect of water on the microstructure and properties of benzene/[bmim][AOT]/[bmim][BF4] microemulsions

“…3 These properties have also led to intense interest in these materials as novel solvents in a range of electrochemical applications. 4 Particular interest has been shown in the self-aggregation of amphiphilic molecules in the ILs, such as micelles, [5][6][7][8][9] microemulsions, [10][11][12][13][14][15] liquid crystals, 16 ion gels, 17 and vesicles. 18 The microstructure and unique properties of these aggregates have been significantly investigated.…”

Supramolecular Structures in the Presence of Ionic Liquids

“…This formation of aqueous droplets in the IL is attributed to the hydrophobic effects between the AOT tails and the long hydrocarbon chain of IL and the strong tendency of the AOT head group to interact with water. In addition, amphiphilic Pluronic polymers were found to be able to form well defined micelles in IL, the micellization was found to be entropy driving (He et al, 2006;Inoue & Misono, 2008;Ueki et al, 2009;Zhang et al, 2008e). ILs have also been found to influence the formation of micelles as co-surfactant.…”