Transition of Ionic Liquid [bmim][PF6] from Liquid to High-Melting-Point Crystal When Confined in Multiwalled Carbon Nanotubes

Physical Properties of the Ionic Liquids (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 (1)they are used in huge amounts and (2)they are usually volatile liquids that are difficult to contain. Welton, T. Chem. Rev. 1999, 99, 2071-2083.

Crystallization of Low-Melting Ionic Liquids collected at -100 oC Winterton, N. et. al. J. Am. Chem. Soc. 2005, 127, 16792-16793.

Ice Nanotubes Inside Carbon Nanotubes Koga, K. et. al. Nature. 2001, 6, 802-805.

Impregnated Nanotubes with IL

Synthesis for IL@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) Electron diffraction 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.