Synthesis and mesomorphic behavior of benzothiazole-based liquid crystals having terminal methoxyl group

A homologous series of benzothiazole derivatives, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, were synthesized and characterized using FT-IR, ¹H and ¹³C NMR, mass spectrometry and elemental analysis. Enantiotropic nematic phase was observed throughout the entire series. Smectic C phase only emerged from the decanoyloxy derivative onwards. The terminal methoxyl group and the ester linkage influenced the mesomorphic behavior of the present series.     

Synthesis and characterization of novel thermotropic liquid crystals containing a dimethylamino group

Novel thermotropic liquid crystals containing a terminal dimethylamino group were synthesized via a multi-step route. Three phenyl ring units linked with ester and azomethine groups constituted the mesogenic core. All the compounds were characterized by spectroscopic techniques, polarizing microscopy and differential scanning calorimetry. An enantiotropic nematic phase was observed for all the systems studied.     

Mesomorphic behavior of new azomethine liquid crystals having terminal iodo group

A series of azomethine esters,3-hydroxy-4-{[（4-iodophenyl）imino]methyl}phenyl alkanoates possessing even number of carbon atoms at the terminal alkanoyloxy chain(C_n-1H_2n-1COO-,n = 4,6,8,10,12,14) was synthesized.n-Butanoyloxy was found non-mesogenic,whilst n-hexanoyloxy to n-tetradecanoyloxy exhibited enantiotropic smectic A phase with fan-shaped texture.It was found that the length of terminal alkanoyloxy chain influenced the mesomorphic properties.     

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.     

Synthesis and characterization of novel fluorinated bistolane-type liquid crystals

Three series of fluorinated bistolane-type liquid crystals have been synthesized. Their mesomorphic properties were studied by optical polarizing microscopy and DSC. These compounds exhibit only a broad nematic phase with high clearing points, wide phase transition temperatures and low melting points. The effects of lateral fluoro-substitution and the introduction of the tetrafluorophenylene moiety are discussed in detail.     

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 characterization of novel fluorinated bistolane-type liquid crystals

Three series of fluorinated bistolane-type liquid crystals have been synthesized. Their mesomorphic properties were studied by optical polarizing microscopy and DSC. These compounds exhibit only a broad nematic phase with high clearing points, wide phase transition temperatures and low melting points. The effects of lateral fluoro-substitution and the introduction of the tetrafluorophenylene moiety are discussed in detail.     

Synthesis and mesomorphic behaviour of novel light-emitting liquid crystals

We report the results of a systematic study of the structure-mesomorphic behaviour relationships of a diverse range of light-emitting liquid crystals, but especially nematic 2,7-disubstituted-9,9-dialkylfluorenes. The dependence of the mesomorphic behaviour and transition temperatures on the nature and length of the terminal chains, the nature, position and number of lateral substituents and the number and nature of aromatic rings with and without heteroatoms in the central core is studied. The results of these studies are used to design polymerizable, light-emitting crystals (reactive mesogens) with a nematic phase having a high clearing point and a melting point below room temperature for facile OLED fabrication.     

Synthesis and characterization of novel fluorinated diphenyldiacetylenic liquid crystals

Five series of asymmetric diphenyldiacetylenes containing a single fluorine, two fluorines or a trifluoromethyl group at one end and an alkyl, alkyloxy or alkenyloxy group on the other end, were prepared and characterized. Most of the 4-alkylphenyl-4'-fluorophenyldiacetylenes, 4-alkyloxyphenyl-4'-fluorophenyldiacetylenes and 4-alkenyloxyphenyl-4'-fluorophenyldiacetylenes obtained exhibit an enantiotropic nematic phase and no smectic phase. However, most of the 4-alkyl-3', 4'-difluorodiphenyldiacetylenes, 4-alkenyloxy-3',4'-difluorodiphenyldiacetylenes and 4-alkyl-4'-trifluoromethyldiphenyldiacetylenes show no mesomorphic behaviour. The effects of alkyl, alkyloxy, alkenyloxy, fluoro, 3,4-difluoro and trifluoromethyl end groups on the mesomorphic behaviour of the diphenyldiacetylenes prepared are discussed.     

A novel ferroelectric liquid crystal having a trifluoromethyl group at the chiral centre

A novel ferroelectric liquid crystal (FLC), 4-(1,1,1-trifluoro-2-octyl)phenyl 4'-nonyloxybiphenyl-4-carboxylate has been synthesized using optically active 4,4,4-trifluoro3-(4-methoxyphenyl)butanoic acid. Although the FLC seemed to satisfy an empirical rule for a large spontaneous polarization (Ps) value, the observed maximum Ps value, c. 100 nCcm-2, was not as large as expected. However a relatively short response time of 68 mus at 50 C was observed.     

Synthesis and characterisation of reactive liquid crystals containing an azo group

A new series of liquid crystal (LC) monomers – not only contain a double bond but also contain an azo group – were designed and synthesised. The length of side groups in the LC monomers containing azobenzene ester varied from 1 to 2 methylene units, and the length of the substituted groups in the main chain varied from 1 to 3 methylene units. The molecular structures of the intermediates and target compounds were confirmed by Fourier transform infrared, ultraviolet and visible spectrum and nuclear magnetic resonance (NMR) spectroscopy. The thermal phase behaviour of the LC monomers was investigated by polar optical microscopy coupled with hot stage and differential scanning calorimetry (DSC). In this paper, the effect on the LC zone with the substituents were investigated, and with the increased methylene of main chain, the melting point and the phase transition temperature of the substance will be lowered and LC regions will be narrower.     

Mesomorphic behavior of new benzothiazole liquid crystals having Schiff base linker and terminal methyl group

正A homologous series of heterocycles,6-methyl-2-(4-alkoxybenzylidenamino)benzothiazoles,were synthesized and characterized using FT-IR,~1H and ~(13)C NMR and mass spectrometric analysis.Enantiotropic nematic phase was observed for shorter members.Smectic A phase only emerged from octyloxy derivative onwards.The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series.     

Synthesis of novel nematic liquid crystals containing 3,3'-dimethyl-2,2'-bipyridyl

Liquid-crystalline 3,3′-dimethyl-2,2′-bipyridyl derivatives with long 4-(alkoxyphenyl)ethynyl (-C≡C-C₆H₄-OR) groups in the 5,5′-positions were synthesized by palladium-catalysed crosscoupling reactions. The compounds exhibit exclusively nematic behaviour; for example, the hexyl derivative showed a nematic phase over the temperature range 145.2–205.0°C. On increasing the length of the terminal chain, the transition temperatures were lowered; for example, the hexadecyl derivative was nematic in the range 117.0–126.8°C.     

Synthesis of novel nematic liquid crystals containing 3,3'-dimethyl-2,2'-bipyridyl

Liquid-crystalline 3,3'-dimethyl-2,2'-bipyridyl derivatives with long 4-(alkoxyphenyl)ethynyl (-C=C-C₆H₄-OR) groups in the 5,5'-positions were synthesized by palladium-catalysed crosscoupling reactions. The compounds exhibit exclusively nematic behaviour; for example, the hexyl derivative showed a nematic phase over the temperature range 145.2-205.0°C. On increasing the length of the terminal chain, the transition temperatures were lowered; for example, the hexadecyl derivative was nematic in the range 117.0-126.8°C.     

New ferroelectric liquid crystals having a trifluoromethyl group at the asymmetric centre and a three-ring heterocyclic core

New ferroelectric liquid crystals with a trifluoromethyl group at the asymmetric centre and a three-ring heterocyclic core have been synthesized. These compounds possessed a large spontaneous polarization and exhibited a S*_c phase over a wide temperature range. Their properties were largely affected by the structure of the spacer group and the core part.     

Synthesis and mesomorphic properties of four-ring fluorinated liquid crystals with trifluoromethyl group

The discovery of nematic phase in 3-fluoro-4-trifluoromethyl-4?-(4?-alkyl [trans, trans-1,1?-bicyclohexyl]-4-yl) 1,1?-biphenyls (n = 2, 3, 4, 5) is an accidental affair. A convenient method was used for the synthesis of these target compounds. After the preparation of the intermediate with trifluomethyl group, the target compounds were synthesised by Suzuki cross-coupling reaction. Then, these phase transition temperatures were measured by polarising textural observation, which confirmed the existence of single nematic phase. These temperatures were also measured by differential scanning calorimetry, which showed that the clearing point of compound (n = 3) is 267℃. The possible mechanism of occurrence of unique nematic phase was discussed on the basis of the principles of fluorine chemistry.     

Synthesis and characterization of polymerizable photochromic liquid crystals containing a spiro-oxazine group

Novel polymerizable photochromic liquid crystal materials containing either the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]naphth[2,1-b][1,4]oxazine] group or the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[3,2-f][1,4]benzoxazine] group as the photochromic moiety, and the biphenylene unit as the mesogenic moiety, were synthesized. Thermal and physical properties of the compounds were examined using differential scanning calorimetry, optical polarizing microscopy, wide-angle X-ray diffractometry and UV-visible spectrophotometry. The photochromic compounds containing both photochromic and mesogenic moieties showed metastable mesophases; These tended to crystallize with time and on heating. The crystallization behaviours were strongly dependent on the structure of the terminal group of alkylene spacer and the position of the spiro-oxazine bound to the mesogen.     

Some novel cholesteric liquid crystals

Abstract

We investigate the possibility of inferring the absence of an ordered phase using Monte Carlo simulations. The example we have chosen is that of a one dimensional Lebwohl-Lasher model, where an analytic solution is available. We argue that Monte Carlo can be of help even in this delicate sector notwithstanding the complications created by periodic boundary conditions.     

Some novel cholesteric liquid crystals

A novel series of cholesteric liquid crystals (CNTⁿ). made by quaternization of the new mesogenic unit cholesteryl isonicotinate (CN) with n-alkyl salts, C_nH_2n + ₁ (T) (n = 2 to 8, T = 4-MeC₆H₄SO₃) has been prepared. Differential scanning calorime-try and polarizing optical microscopy studies reveal that all of these salts exhibit an enantiotropic cholesteric phase but for the cholesteryl isonicotinate unit the cholesteric phase is monotropic. For all members of the series the cholesteric-isotropic transitions are not reversible as these salts begin to decompose before their cholesteric-isotropic transition point is reached.     

Some novel disaccharide-derived liquid crystals

Some novel disaccharide-derived amphiphiles, in which the hydrophobic long chain alkyl group and an alpha -D-glucose moiety are separated by a hydrophilic five carbon spacer or a hydrophobic furan residue, were investigated as to their mesomorphic properties using DSC, thermomicroscopy and various X-ray methods. All compounds exhibit a smectic A phase, characterized by aggregation to a bilayered S structure. The layer thickness d , measured by A X-ray, correlates with the presence of polar d and non-polar moieties, adjoining molecules interacting via hydrogen bonding. Based on the known structural concepts for sugar-derived liquid crystals, a model is suggested to account for the observed S mesomorphic behaviour of two N -alkanoyl derivatives of (glucosylox dymethylfuryl) methylamine, i.e. species in which sugar and long chain fatty acid are separated by a quasi-aromatic furan residue, is unusual, as different X-ray methods invariably give the same odd indicative of a smectic layer thickness of three to four molecules. layer arrangement. The A d -value indicative of a smetic layer thickness of three to four molecules.