Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
Chemistry. 2012 Mar 5;18(10):3014-22. doi: 10.1002/chem.201101925. Epub 2012 Feb 1.
Ionic liquid crystals are mesogenic compounds that consist of cations and anions, usually rod-like cations and spherical anions. Herein we report a new method for the synthesis of ionic liquid crystals by using cations and anions of the same molecular shape with oppositely charged head groups. Thus, 4-alkoxyphenylpentamethylguanidinium 4-alkoxyphenylsulfonate ion pairs have been synthesised. 4-Alkoxyphenylpentamethylguanidinium iodides were also prepared to determine the influence of congruently shaped anions, in comparison with their spherical counterparts, on mesophase behaviour, which was investigated by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction (XRD). All the liquid crystalline salts exhibit smectic A mesophases with strongly interdigitated bilayer structures. The guanidinium sulfonate ion pairs show mesomorphic properties from shorter alkyl chain lengths (≥C(9)) and lower melting points (≈10 K), whereas the corresponding guanidinium iodides are liquid crystalline for longer alkyl chain lengths (≥C(14)). For chains with ≥C(18), however, the mesophase range decreases for the sulfonate ion pairs, but not for the iodide salts.
离子液晶是由阳离子和阴离子组成的中间相化合物，通常为棒状阳离子和球形阴离子。在此，我们报告了一种通过使用带有相反电荷头基的相同分子形状的阳离子和阴离子来合成离子液晶的新方法。因此，合成了 4-烷氧基苯基戊甲基胍 4-烷氧基苯基磺酸盐离子对。还制备了 4-烷氧基苯基戊甲基碘化胍，以确定与球形阴离子相比，形状一致的阴离子对介相行为的影响，通过差示扫描量热法（DSC）、偏光显微镜（POM）和 X 射线衍射（XRD）研究了介相行为。所有液晶盐均表现出强交错双层结构的近晶 A 相。胍磺酸盐离子对具有较短烷基链长度（≥C(9)）和较低熔点（≈10 K）的介晶性质，而相应的胍碘化物则具有较长烷基链长度（≥C(14)）的液晶性质。然而，对于 ≥C(18)的链，磺酸盐离子对的介相范围减小，但碘化物盐则没有。
