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首页> 外文期刊>Chemistry: A European journal >Tyrosine-Based Ionic Liquid Crystals: Switching from a Smectic A to a Columnar Mesophase by Exchange of the Spherical Counterion
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Tyrosine-Based Ionic Liquid Crystals: Switching from a Smectic A to a Columnar Mesophase by Exchange of the Spherical Counterion

机译：酪氨酸基离子液晶：通过交换球形抗衡离子从近晶A转变为柱状中间相

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摘要

Synthetic strategies were developed to prepare l-tyrosine-based ionic liquid crystals with structural variations at the carboxylic and phenolic OH groups as well as the amino functionality. Salt metathesis additionally led to counterion variation. The liquid-crystalline properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS, SAXS). The symmetrical ILC chlorides bearing the same alkyl chain at both the ester and ether but either an acyclic or cyclic guanidinium group displayed enantiotropic SmA(2) mesophases with phase widths of 31-88K irrespective of the head group. It was particularly the replacement of chloride in the acyclic guanidinium ILC by hexafluorophosphate that induced a phase change from SmA(2) to Col(r). This phase change was attributed to a higher curvature of the interface due to the larger anion, which increased the effective head group cross-sectional area of the amphiphilic ILC. The unsymmetrical acyclic guanidinium chlorides, bearing a constant C-14 ester and variable alkyl chains on the phenolic position, formed enantiotropic SmA(2) phases. The derivative with the largest difference in chain lengths, however, displayed a Col(r) phase, resulting from discoid aggregates of the cone-shaped guanidinium chloride. The results are discussed in terms of the packing parameters, which indicate that the phase behaviour of the thermotropic tyrosine-based ILCs shows analogies to those of lyotropic liquid crystals.
机译：已开发出合成策略以制备在羧基和酚羟基以及氨基官能团上具有结构变化的基于I-酪氨酸的离子液晶。盐复分解另外导致抗衡离子变化。通过差示扫描量热法（DSC），偏振光学显微镜（POM）和X射线衍射（WAXS，SAXS）研究了液晶性质。对称的ILC氯化物在酯和醚上均具有相同的烷基链，但无环或环状胍基均显示对映SmA（2）中间相，无论头基如何，相宽为31-88K。尤其是六氟磷酸酯取代了无环胍盐ILC中的氯化物，引起了从SmA（2）到Col（r）的相变。这种相变归因于较大的阴离子，这是由于界面的曲率较高，从而增加了两亲性ILC的有效头基横截面积。不对称的无环胍盐氯化物，在酚醛位置上带有恒定的C-14酯和可变的烷基链，形成对映SmA（2）相。然而，链长差异最大的衍生物表现出Col（r）相，这是由锥形氯化胍的盘状聚集体产生的。根据填充参数对结果进行了讨论，这些参数表明基于热致酪氨酸的ILC的相行为类似于溶致液晶。

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