Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (4): 653-659.doi: 10.3866/PKU.WHXB201502031

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Influence of Intermolecular Interactions on the Mesogenic Properties of Imidazolium Salts

WANG Meng1, PAN Xu1, DAI Song-Yuan1,2, CHEN Jian1   

  1. 1 Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, P. R. China;
    2 Beijing Key Laboratory of Novel Thin Film Solar Cell, North China Electric Power University, Beijing 102206, P. R. China
  • Received:2014-11-21 Revised:2015-02-02 Published:2015-04-03
  • Contact: PAN Xu, DAI Song-Yuan E-mail:mars_dark@Hotmail;sydai@ipp.ac.cn
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2011CBA00700), National High Technology Research and Development Program of China (863) (2011AA050510), National Natural Science Foundation of China (21103197, 21273242), National Science Foundation for Post-doctoral Scientists of China (2013M540526).

Abstract:

Aseries of imidazolium salt-based ionic liquid crystals with a smectic A(SmA) phase are synthesized by altering the substituents attached to the 1-position (N1) and 3-position (N3) of the imidazolium ring, and anions. The mesogenic properties of the imidazolium salts, including mesophase temperature range and structural properties, are studied by differential scanning calorimetry, small-angle X-ray diffraction, and single crystal diffraction. The anisotropic ion conductivities of several ionic liquid crystals are also measured. It is found that substituents attached to N1 or N3 and the anions influence the van der Waals interactions and hydrogen bond, which results in a significant effect on the mesogenic properties of the imidazolium salts. Moreover, when a vinyl group is attached to the N3 position, π-π stacking interactions form between adjacent layers. This not only benefits the formation of a mesophase but also results in the biggest layer spacing and lowest anisotropic ion conductivities for imidazolium tetrafluoroborates. These results suggest that all intermolecular interactions should be taken into account when regulating the mesogenic properties of ionic liquid crystals.

Key words: Imidazolium salts, Mesogenic property, van der Waals interaction, Hydrogen bond, π-π stacking

MSC2000: 

  • O641