First mesomorphic and DFT characterizations for 3- (or 4-) n-alkanoyloxy benzoic acids and their optical applications

New liquid crystalline hydrogen bonded 3- (or 4)-n-alkanoyloxy benzoic acids were synthesized and probed theoretically and experimentally. The molecular structures of these compounds were elucidated by proton NMR, carbon-13 NMR and elemental analyses. Differential scanning calorimetry (DSC) was used to investigate the thermal and mesomorphic properties of all the symmetrical dimers that bearing identical alkanoyloxy chains. Moreover, polarized optical microscopy (POM) was used to determine their mesophases. The findings show that all the designed symmetrical dimers exhibit the smectic mesophase with relative thermal stability that depends on the length of their terminal side chain. Additionally, the experimental findings of the mesomorphic behavior are further supported by DFT calculations. The alkanoyloxy benzoic acid para-derivatives (In) were shown to be more stable than their meta-substituted (IIn) analogues due to stronger hydrogen bonding interactions. The computed reactivity parameters showed that the position of ester moiety has a significant impact on the acids reactivity. The absorbance spectra of both the 3- (or 4)-n-alkanoyloxy benzoic acids revealed a blue shift with the increment of the of alkyl chain size; however, the energy band gaps of 3-n-alkanoyloxy benzoic derivatives were found to be slightly higher than those of the 4-n-alkanoyloxy benzoic acids. Moreover, the photoluminescence spectrum of the prepared materials is rather broad, and exhibited a red shift as the alkyl chain length increases. The fluorescence lifetime shown to rise as alkyl chain length grows longer, and 3-n-alkanoyloxy benzoic acids have slightly longer lifetime compared to their 4-n-alkanoyloxy benzoic analogues.

Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway

We have prepared a series of pyridinium-based gemini amphiphiles. They exhibit thermotropic liquid–crystalline behavior depending on their alkyl chain lengths and anion species. By adjusting the alkyl chain lengths and selecting suitable anions, we have obtained an ionic amphiphile that exhibits a normal-type bicontinuous cubic phase from 38 °C to 12 °C on cooling from an isotropic phase. In the bicontinuous cubic liquid–crystalline assembly, the pyridinium-based ionic parts align along a gyroid minimal surface forming a 3D continuous ionic domain while their ionophobic alkyl chains form 3D branched nanochannel networks. This ionic compound can form homogeneous mixtures with a lithium salt and the resultant mixtures keep the ability to form normal-type bicontinuous cubic phases. Ion conduction measurements have been performed for the mixtures on cooling. It has been revealed that the formation of the 3D branched ionophobic nanochannels does not disturb the ion conduction behavior in the ionic domain while it results in the conversion of the state of the mixtures from fluidic liquids to quasi-solids, namely highly viscous liquid crystals. Although the ionic conductivity of the mixtures is in the order of 10–7 S cm–1 at 40 °C, which is far lower than the values for practical use, the present material design has a potential to pave the way for developing advanced solid electrolytes consisting of two task-specific nanosegregated domains: One is an ionic liquid nano-domain with a 3D continuity for high ionic conductivity and the other is ionophobic nanochannel network domains for high mechanical strength.

Ionic N-phenylpyridinium tetracatenar mesogens: competing driving forces in mesophase formation and unprecedented difference in phase stabilisation within a homologous series

Ionic, tetracatenar liquid crystals containing an N-phenylpyridinum core are described; many of these compounds display a SmA phase, something extremely rare in tetracatenar materials. The competing forces driving mesophase formation lead to an unprecedented difference in phase stabilities for SmA and Colh phases.

Dimension control of ionic liquids

Ionic liquids have established themselves as promising soft compounds for bringing innovation to materials science. For further developing functions and abilities of ionic liquids, one of the most important challenges is to organize ionic liquids into dimensionally ordered states. In this feature article, we will present the organization of ionic liquids by endowing them with liquid-crystalline properties. In particular, focusing on the specific abilities and properties of functional ionic liquids, a variety of nanostructured ionic materials have been developed and their unique and enhanced functions have been revealed. Some potential uses of organized ionic liquids have also been mentioned.

Selective lithium ion recognition in self-assembled columnar liquid crystals based on a lithium receptor

Lithium is recognized as being significantly important due to its various applications in different areas especially in energy technology. In the present study, self-assembled nanostructured liquid-crystalline (LC) materials, that selectively bind lithium cations, have been developed for the first time. Wedge-shaped crown ether derivatives bearing dibenzo-14-crown-4 (DB14C4) or 12-crown-4 moieties are able to act as LC lithium-selective receptors. We have found that complexation of these receptors with lithium perchlorate induces liquid-crystalline columnar phases, while sodium perchlorate is immiscible with both receptors. Remarkably, a receptor consisting of DB14C4 as an effective lithium-selective ligand exhibits high selectivity for LiCl over NaCl, KCl, RbCl and CsCl. The lithium selectivity was demonstrated and investigated by ¹H NMR, ¹H COSY and FT-IR spectroscopic measurements. The preferred coordination number of four and the ideal cavity geometry of the DB14C4 moiety of the receptor are shown to be key factors for the high lithium selectivity. This new design of LC lithium-selective receptors opens unexplored paths for the development of methods to fabricate nanostructured materials for efficient selective lithium recognition.

Development of Glassy Bicontinuous Cubic Liquid Crystals for Solid Proton-Conductive Materials

Glassy bicontinuous cubic liquid crystals are developed to be a matrix having a hydrophilic infinite periodic minimal surface (IPMS). They function as a scaffold for water, leading to the formation of a 3D continuous hydrogen-bonding network of water molecules along the IPMS. This material design is advantageous for developing novel electrolytes with rigidity and high proton conductivity.

Bis-imidazolium salts with alkyl sulfates as counterions: synthesis and liquid crystalline properties

A series of flexibly linked bis-imidazolium salts with alkyl sulfate anions having different chain lengths (10, 12, 14) was investigated for their thermotropic behavior.

Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals

A novel ionic mixture of an imidazolium-based room-temperature ionic liquid containing ethylene-oxide-functionalized phosphite anions is fabricated, which, when doped with lithium salt, self-assembles into a smectic-ordered ionic liquid crystal through Coulombic interactions between the ion species. Interestingly, the smectic order in the ionic-liquid-crystal ionogel facilitates ionic transport.

Ionic Liquid Crystals: Versatile Materials

This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.

Liquid crystals based on silver carbene complexes derived from dimeric bis(imidazolium) bromide salts

Liquid crystalline bis(imidazolium) salts with different mesogenic groups (cyanobiphenyl or cholesteryl) and their silver carbene complexes with Br⁻ anion with blue emission have been designed and studied.

Synthesis of guanidinium-sulfonimide ion pairs: towards novel ionic liquid crystals

The recently introduced concept of ionic liquid crystals (ILCs) with complementary ion pairs, consisting of both, mesogenic cation and anion, was extended from guanidinium sulfonates to guanidinium sulfonimides. In this preliminary study, the synthesis and mesomorphic properties of selected derivatives were described, which provide the first example of an ILC with the sulfonimide anion directly attached to the mesogenic unit.