Synthesis and mesomorphic properties of fluoro and isothiocyanato biphenyl tolane liquid crystals

Four series of high birefringence biphenyl tolane liquid crystals having a terminal isothiocyanato or fluoro group were synthesized; their mesomorphic properties were studied by optical polarizing microscopy and DSC. These biphenyl tolane compounds exhibit reasonably low melting points and high birefringence of 0.37–0.49. By using these compounds a eutectic mixture was formulated exhibiting a wide nematic range, high figure‐of‐merit and low viscosity.     

Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals

Four series of high birefringence bistolane liquid crystals containing isothiocyanato termal groups were synthesized and characterized. As well as the phenyl group, both biphenyl and naphthyl moieties were introduced to enhance the birefringence. These bistolane compounds exhibit reasonably low melting points and high birefringence of 0.5-0.8. A eutectic mixture was formulated from these compounds exhibiting a wide nematic range, high figure-of-merit and low viscosity.     

Synthesis and mesomorphic properties of novel tetrafluorinated biphenyl acetylene liquid crystals with a blue phase

Five novel tetrafluorinated biphenyl acetylene molecules containing two chiral centres in the side chain were synthesized. The mesomorphic behaviour of these compounds was characterized by differiential scanning calorimetry (DSC) and optical polarizing microscopy. All these compounds exhibit cholesteric and blue phases.     

Synthesis and mesomorphic properties of novel tolane-type liquid crystals

Two series of novel tolane-type liquid crystals(LCs) comprising of hydrogen-bonded organic acids were synthesized.The formation of dimerized H-bond LCs was confirmed by IR spectroscopy,and mesomorphic properties of the LCs were investigated by differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).It was found that the end groups of the liquid crystals as well as the unsaturated rigid core had effect on the mesomorphic properties.     

Synthesis and mesomorphic properties of semi-perfluorinated chain liquid crystals

Three homologous series of 4-(n-polyfluoroalkoxycarbonyl)phenyl 4-[(4-n-alkoxyphenyl)ethynyl] benzoates have been synthesized from 1,1,3-trihydroperfluoropropanol, 1,1,5-trihydroperfluoropentanol and 1,1,7-trihydroperfluoroheptanol. Polarizing microscopic textural observations and DSC measurements of the phase transitions of these compounds show that most of them are thermotropic liquid crystals with smectic A and very broad smectic C phases; furthermore, several show very narrow monotropic SmB phases. The effect of the terminal polyfluoroalkoxy and alkoxy groups on the mesomorphic behaviour is also discussed.     

Synthesis and mesomorphic properties of chiral fluorinated liquid crystals

Some fluorinated chiral liquid crystals were synthesized and the compounds characterized by IR, ¹H NMR, ¹⁹F NMR and mass spectroscopy and elemental analysis. Their phase transition behaviour was investigated by differential scanning calorimetry and polarizing optical microscopy. Nearly all of the compounds synthesized are liquid crystals with an enantiotropic cholesteric phase. Some of them exhibit a blue phase. Lateral tetrafluoro substitution decreases the clearing point and molecular polarity affects the formation of liquid crystalline phases.     

Synthesis and mesomorphic properties of fluoro-containing azobenzene liquid crystals

Four series of azobenzene liquid crystal compounds containing a fluorinated tolan unit have been synthesized. The mesomorphic behaviours of these compounds were characterized by differential scanning calorimetry and optical polarizing microscopy. The compounds of these series exhibit a nematic, a smectic C or a smectic B phase. This investigation revealed that the alkoxy chain at the side of the azobenzene moiety plays a more important role in the formation of smectic phases than the one at the side of the tolan moiety.     

Synthesis and mesomorphic properties of three-benzene-ring-containing banana-shaped liquid crystals

A homologous series of three-benzene-ring-containing banana-shaped compounds, N,N-bis(4-alkylcarbonyloxybenzylidene)benzene-1,3-diamine, were synthesised by esterifying aliphatic acids with the three-benzene-ring bent core 1,3-phenylene-bis(4-hydroxybenzylideneamine). As the number of carbon atoms in the aliphatic acids increased from 1 to 12, 12 novel banana-shaped compounds resulted with increasing lengths in their terminal tails. The mesomorphic properties of this homologous series of three-benzene-ring-containing banana-shaped compounds were characterised by means of polarised optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies. Our results have demonstrated that this series of banana-shaped compounds can form mesophases, although each of their bent cores contains only three benzene rings.     

Synthesis and mesomorphic properties of fluoro-containing azobenzene liquid crystals

Four series of azobenzene liquid crystal compounds containing a fluorinated tolan unit have been synthesized. The mesomorphic behaviours of these compounds were characterized by differential scanning calorimetry and optical polarizing microscopy. The compounds of these series exhibit a nematic, a smectic C or a smectic B phase. This investigation revealed that the alkoxy chain at the side of the azobenzene moiety plays a more important role in the formation of smectic phases than the one at the side of the tolan moiety.     

Synthesis and mesomorphic properties of new azine-type liquid crystals

A series of symmetrical azine-type liquid crystals were synthesized. The characteristic of these liquid crystals is that they had high clearing point ( ～320 ℃) and broad thermal range of nematic phase ( ～154 ℃). It was also found that the end groups of the liquid crystals had effect on the mesomorphic properties.     

Synthesis and mesomorphic properties of chiral fluorinated liquid crystals

Some fluorinated chiral liquid crystals were synthesized and the compounds characterized by IR, ¹H NMR, ¹⁹F NMR and mass spectroscopy and elemental analysis. Their phase transition behaviour was investigated by differential scanning calorimetry and polarizing optical microscopy. Nearly all of the compounds synthesized are liquid crystals with an enantiotropic cholesteric phase. Some of them exhibit a blue phase. Lateral tetrafluoro substitution decreases the clearing point and molecular polarity affects the formation of liquid crystalline phases.     

Synthesis and mesomorphic properties of rigid-core ionic liquid crystals

Ionic liquid crystals combine the unique solvent properties of ionic liquids with self-organization found for liquid crystals. We report a detailed analysis of the structure-property relationship of a series of new imidazolium-based liquid crystals with an extended aromatic core. Investigated parameters include length and nature of the tails, the length of the rigid core, the lateral substitution pattern, and the nature of the counterion. Depending on the molecular structure, two mesophases were observed: a bilayered SmA2 phase and the more common monolayered SmA phase, both strongly interdigitated. Most materials show mesophases stable to high temperatures. For some cases, crystallization could be suppressed, and room-temperature liquid crystalline phases were obtained. The mesomorphic properties of several mixtures of ionic liquid crystals were investigated. Many mixtures showed full miscibility and ideal mixing behavior; however, in some instances we observed, surprisingly, complete demixing of the component SmA phases. The ionic liquid crystals and mixtures presented have potential applications, due to their low melting temperatures, wide temperature ranges, and stability with extra ion-doping.     

Heterocyclic benzoxazole-based liquid crystals:Synthesis and mesomorphic properties

New Schiff base liquid crystals containing benzoxazole core and alkanoyloxy chain at the end group of the molecules (C_n-1H_2n-1COO-,n=14,16,18) was synthesized.The present compounds are enantiotropic smectic A liquid crystals.It was also found that the end groups of the molecules and polar chloro substituent at the benzoxazole fragment had effect on the mesomorphic properties.     

Synthesis and mesomorphic properties of two semi-fluorocarbon chain liquid crystals

Two chiral molecules, each having a long fluoroalkylalkoxy chain, have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by differential scanning calorimetry. Very broad SmC* phase is found in one of these two compounds.     

Synthesis and mesomorphic properties of two semi-fluorocarbon chain liquid crystals

Two chiral molecules, each having a long fluoroalkylalkoxy chain, have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by differential scanning calorimetry. Very broad SmC* phase is found in one of these two compounds.     

Synthesis and properties of allyloxy-based tolane liquid crystals with high negative dielectric anisotropy

A series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (?4.44) and a broad nematic mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.     

Synthesis and mesomorphic properties of some ferroelectric liquid crystals of lactate

A semiperfluorinated chain has been introduced into three series of lactate‐based molecules, and their mesomorphic properties have been studied by DSC and optical polarized microscope. An abnormal phenomenon has been found that the introduction of a triple bond in the core of the molecule, which lengthened the molecule, gave rise to a decrease in the thermal stability of chiral smectic C phase and smectic A phase. 2, 3‐Difluoro substituents of the phenylenic structure hinder the formation of the chiral smectic C phase because of the steric effect.     

Synthesis and mesomorphic properties of steroidal liquid crystals containing perfluoroalkoxycarbonylphenyl units

Two cholesteryl esters liquid crystals containing perfluoroalkoxy terminal chains, and benzoate and carbonate moieties, have been synthesized. Their mesomorphic properties were observed and measured by optical polarizing microscopy and differential scanning calorimetry. The results show that the two liquid crystals exhibit smectic A and B phases. No chiral tilted smectic phase was observed.     

Synthesis and mesomorphic properties of chiral liquid crystals having thiolactate groups

A homologous series of chiral thiolactate liquid crystals, alkyl 2-[4-(4-decyloxyphenyl)benzoyloxyphenyloxy]thiopropionates, ADBPT-n (n=2-6), was prepared from (R)-2-(4-hydroxyphenoxy)propionic acid. Structural effects on the mesomorphic and physical properties were investigated in terms of variation in the length of alkyl chain attached to the thiolactate group. The mesophases and their corresponding transition temperatures were identified by polarizing optical microscopy and differential scanning calorimetry. Compound ADBPT-4 exhibited SmA* and SmC* phases, whereas other compounds in the series exhibited the SmA* phase along with unidentified SmX₁* and SmX₂* phases. The maximum P_s value measured for ADBPT-4 in the SmC* phase was 17.5 nC cm^-2, suggesting the polarization of the material is rather low. The tilt angles were also measured, reaching a maximum of 48 degree.