Regulating mesogenic properties of ionic liquid crystals by preparing binary or multi-component systems
作者:Meng Wang、Xu Pan、Shangfeng Xiao、Changneng Zhang、Wenxin Li、Songyuan Dai
DOI:10.1039/c1jm14790k
日期:——
In this study, a series of binary systems based ionic liquid crystals (ILCs) C12MIm(BF4)yIx (x + y = 1) are prepared by mixing ILCs 1-dodecyl-3-methylimidazolium iodide (C12MImI) and 1-dodecyl-3-methylimidazolium tetrafluoroborate (C12MImBF4), aiming to combine the properties of both C12MImBF4 and C12MImI. Their mesogenic properties are characterized by thermal analysis, polarized optical microscopy, X-ray diffraction as well as anisotropic ionic conductivity measurements. It is found that the smectic A phase with interdigitated bilayer structure is observed in the C12MIm(BF4)yIx series. The binary system C12MIm(BF4)yIx has a larger mesophase temperature range and interdigitated layer spacing than pure C12MImBF4. And the anisotropic ionic conductivity of the binary system, including parallel and perpendicular to smectic layer, is higher than pure C12MImI. Moreover, in binary system C12MIm(BF4)yIx, with the increasing content of C12MImI the ability of the anion to form three dimensional hydrogen bonds increases, resulting in the increase of the mesophase temperature range, interdigitated layer spacing and the decrease of anisotropic ionic conductivity. Furthermore, multi-component system based ILCs are obtained by introducing iodine to the binary system, and the mesophase temperature range is lowered, which is associated with the weak ability of I3− to form hydrogen bond with cations. All these results suggest that we can regulate the mesogenic properties of ILCs as we need by making binary or even multi-component systems.
本研究通过混合 1-十二烷基-3-甲基碘化咪唑鎓(C12MImI)和 1-十二烷基-3-甲基四氟硼酸咪唑鎓(C12MImBF4)制备了一系列基于二元体系的离子液体晶体(ILCs)C12MIm(BF4)yIx(x + y = 1),旨在结合 C12MImBF4 和 C12MImI 的特性。通过热分析、偏振光学显微镜、X 射线衍射以及各向异性离子电导率测量,对它们的介电性进行了表征。研究发现,C12MIm(BF4)yIx 系列中出现了具有交错双层结构的共晶 A 相。与纯 C12MImBF4 相比,二元体系 C12MIm(BF4)yIx 具有更大的介相温度范围和交错层间距。而且二元体系的各向异性离子电导率(包括平行和垂直于胶凝层的离子电导率)高于纯 C12MImI。此外,在二元体系 C12MIm(BF4)yIx 中,随着 C12MImI 含量的增加,阴离子形成三维氢键的能力也会增加,从而导致介相温度范围、互晶层间距的增加和各向异性离子导电率的降低。此外,通过在二元体系中引入碘,得到了基于多组分体系的 ILC,介相温度范围降低,这与 I3- 与阳离子形成氢键的能力较弱有关。所有这些结果表明,我们可以通过制造二元甚至多组分体系来根据需要调节 ILC 的介相性质。