Transition of Ionic Liquid [bmim][PF6] from Liquid to High-Me

lting-PointCrystal When Confined in Multi

walled Carbon Nanotubes

(1)they are used in

huge amounts and

(2)they are usually volatile liquids that

are difficult to contain.

(1)They are good solvents for a wide range of both inorganic and organic materials(2)They are often composed of poorly coordinating ions, so they have the potential to be highly polar yet noncoordinating solvents.(3)polar alternative for two-phase systems(4)Ionic liquids are nonvolatile,hence they may be used in high-vacuum systems

Physical Properties of the Ionic Liquids

Welton, T. Chem. Rev. 1999, 99, 2071-2083.

Crystallization of Low-Melting Ionic Liquids

1-butyl-3-methylimidazolium hexafluorophosphate[bmim][PF6]

NHPF6

Winterton, N. et. al. J. Am. Chem. Soc. 2005, 127, 16792-16793.

collected at -100 oC

Ice NanotubesInside Carbon Nanotubes

Koga, K. et. al. Nature. 2001, 6, 802-805.

Impregnated Nanotubes with IL

Synthesis for IL@MWNTs

MWNTs + [bmim][PF6]

sonication

3 hrs, 90oCIL@MWNTs

MWNTs + [bmim][PF6] + methanolsonication

3 hrs, 90oCIL/methanol@MWNTs

Figure 1. TEM images of opened MWNTs (a), IL@MWNTs (b),IL/MeOH@MWNTs (c), and HRTEM image of a small section of an individual tube of IL@MWNTs (d). (Inset) Electrondiffraction of a selected area of an individual nanotube filled with [bmim][PF6].

X-ray Diffraction Pattern

Figure 2. DSC heating curves for MWNTs (a), [bmim][PF6] (b),IL@MWNTs (c), and IL/MeOH@MWNTs (d) at a scan rate of 10 °C/min.

Conclusions

• The author demonstrated for the first time the

crystallization behavior of IL inside MWNTs, resulting in the formation of a stable, polymorphous crystal possessing a melting point of above 200 °C.

• Not only provide a good addition to the development of new types of CNT-based composites, but they also are helpful for the understanding of phase transitions of dimensionally confined environments.