The substituent effect on mesomorphic properties of 4-octyloxyphenyl 4-(4-R-3-nitrobenzoyloxy)benzoates and 4-(4-octyloxybenzoyloxy)phenyl 4-R-3-nitrobenzoates

The thermal properties of 4-octyloxyphenyl 4-(4-R-3-nitrobenzoyloxy) benzo-ates (1) and 4-(4-octyloxybenzoyloxy)phenyl 4-R-3-nitrobenzoates (2) have been examined, where R = hydrogen, halogens, alkyl and alkoxy groups. The derivatives of compound 1 incorporating hydrogen, halogens, methoxy and nitro groups show a smectic A phase having a bilayer arrangement, and the others with a long alkoxy group show the S_A phase with the monolayer arrangement. The derivatives of compound 2 incorporating halogens, and the nitro group show the S_A phase with the monolayer arrangement. The alkoxy derivatives show a smectic C phase as well as the nematic phase. The nitro group at the lateral position tends to increase the ratio of the S_A-N transition temperature to the N-I. The effect of the nitro group on the smectic properties has been discussed in terms of the structural and electrostatic nature of the nitro group.     

The effect of a lateral substituent on the mesomorphic properties of 4-cyanophenyl 4-(4-alkyloxybenzoyloxy)benzoates

The thermal properties of 4-cyanophenyl 4-(4-alkyloxybenzoyloxy)benzoates having a lateral substituent have been examined. Commencing with the nonyloxy homologue the hydrogen derivative shows a smectic A phase having a partially bilayered arrangement (SA_Ad). When the substituents are introduced at position X, the S_Ad phase commences from the octyloxy homologue, and the chlorine and bromine derivatives show an additional S_Ad phase in the low temperature region. When the substituents are introduced at position Y, the S_Ad phase commences either from the undecyloxy or the dodecyloxy homologue, and the nitro derivative shows two tilted phases in the low temperature region. Compounds having a methoxy group at position Z have difficulty in forming the S_Ad phase. The effect of the substituent on the thermal properties of the smectic phases has been discussed in terms of the electrostatic and structural properties of the substituents. A driving force for the formation of the partially bilayered arrangement is also discussed.     

Synthesis and mesomorphic properties of some fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl]benzoates

Eight homologous series of fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl]benzoates have been synthesized. Textural observations by polarizing microscopy and DSC measurements of the phase transitions show that most of these compounds are thermotropic liquid crystals with nematic and smectic A phases; furthermore, several show monotropic high order smectic phases. The results showed that the SmA phase is enhanced with increasing degree of fluorosubstitution on the para- and meta-positions of the terminal phenyl groups. The mesomorphic properties of these compounds are also affected by the direction of ester bonds. The effect of triple bonds is also discussed.     

Synthesis and mesomorphic properties of some fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl]benzoates

Eight homologous series of fluorinated phenyl 4-[(4-n-alkoxyphenyl)ethynyl]benzoates have been synthesized. Textural observations by polarizing microscopy and DSC measurements of the phase transitions show that most of these compounds are thermotropic liquid crystals with nematic and smectic A phases; furthermore, several show monotropic high order smectic phases. The results showed that the SmA phase is enhanced with increasing degree of fluorosubstitution on the para- and meta-positions of the terminal phenyl groups. The mesomorphic properties of these compounds are also affected by the direction of ester bonds. The effect of triple bonds is also discussed.     

Synthesis and mesomorphic properties of 4-[(4-n-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]phenyl fluoro-substituted benzoates

A series of 4-[(4-n-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]phenyl fluoro-substituted benzoate liquid crystals have been synthesized. Their phase transition temperatures have been measured by optical polarizing microscopy and confirmed by DSC. The results show that a highly fluorinated terminal chain impairs mesomorphic properties.     

Synthesis and mesomorphic properties of fluorinated phenyl 4-[(4-n-alkoxy-2,3-difluorophenyl)ethynyl]benzoates

Three series of fluorinated phenyl 4-[(4-n-alkoxy-2,3-difluorophenyl)ethynyl]benzoate liquid crystals have been synthesized. Their phase transition temperatures were measured by texture observation in a polarizing microscope and confirmed by DSC. Their mesomorphic properties and fluoro-substituent effects were studied in detail.     

Synthesis and mesomorphic properties of 4-[(4-n-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]phenyl fluoro-substituted benzoates

A series of 4-[(4-n-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]phenyl fluoro-substituted benzoate liquid crystals have been synthesized. Their phase transition temperatures have been measured by optical polarizing microscopy and confirmed by DSC. The results show that a highly fluorinated terminal chain impairs mesomorphic properties.     

Synthesis and mesomorphic properties of 4-[(4n-alkoxy-2,3-difluorophenyl)ethynyl]phenyl fluoro-substituted benzoates

Three series of novel fluorinated liquid crystals containing a 2,3-difluorotolan unit have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by DSC. The influence of the lateral fluoro-substitution is discussed.     

Synthesis and mesomorphic properties of 4-[(4n-alkoxy-2,3-difluorophenyl)ethynyl]phenyl fluoro-substituted benzoates

Three series of novel fluorinated liquid crystals containing a 2,3-difluorotolan unit have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by DSC. The influence of the lateral fluoro-substitution is discussed.     

The effect of fluorinated terminal chains on the mesomorphic properties of 4,4'-disubstituted phenyl benzoates

A variety of 4,4'-disubstituted phenyl benzoates having a terminal chain containing multifluorine atoms, attached directly to the benzene ring or through an ester group, have been synthesized and their mesomorphic properties determined by hot stage polarizing optical microscopy. These properties were compared to those of the corresponding hydrogenated esters and to other esters containing rigid terminal chains. Usually transition temperatures were higher and mesophase ranges wider than those observed for the parent compounds but no nematic phases were found. Any mesophase seen was usually a smectic A phase sometimes accompanied by a smectic C phase. Crystal E phases were found along with the smectic A phase in alkyl or alkoxy esters having a C₉F₁₉CO₂ chain on the acid side. A first order smectic A-smectic C transition was observed in the ester with CN on the acid side and O₂CC₇F₁₅ on the phenol side. A comparison of the effect of a terminal fluorinated chain and a lateral fluorine group on one set of esters is also included.     

Mesomorphic properties of 4-(polyfluoroalkoxycarbonyl)phenyl 4-(4-n-heptoxy-2,3,5,6-tetrafluorophenyl)benzoates

A series of 4-(polyfluoroalkoxycarbonyl)phenyl 4-(4-n-heptoxy-2,3,5,6-tetrafluorophenyl)benzoates were synthesized and observed using DSC and optical polarizing microscopy. The results show that they are not mesogens. Their mesomorphic properties were compared with similar compounds containing no aromatic fluorine substituents.     

Mesomorphic properties of 4-(polyfluoroalkoxycarbonyl)phenyl 4-(4-n-heptoxy-2,3,5,6-tetrafluorophenyl)benzoates

A series of 4-(polyfluoroalkoxycarbonyl)phenyl 4-(4-n-heptoxy-2,3,5,6-tetrafluorophenyl)benzoates were synthesized and observed using DSC and optical polarizing microscopy. The results show that they are not mesogens. Their mesomorphic properties were compared with similar compounds containing no aromatic fluorine substituents.     

Synthesis and mesomorphic properties of 4-(1,1,7-trihydroperfluoroheptyloxycarbonyl)phenyl 4'-n-alkoxybiphenyl-4-carboxylate

A family of 4-(1,1,7-trihydroperfluoroheptyloxycarbonyl)phenyl 4'-n-alkoxybiphenyl-4-car- boxylates has been synthesized. The compounds show the smectic A phase while the mesogens with intermediate terminal alkyl chain ( n 7-12) also exhibit a broad smectic C phase.     

Synthesis and mesomorphic properties of n-alkyl 4-[4-(4-n-octyloxybenzyloxy-2,3,5,6-tetrafluorophenyl)ethynyl]benzoates

A new series of n-alkyl 4-[4-(4-n-octyloxybenzyloxy-2,3,5,6-tetrafluorophenyl)ethynyl)benzoates have been prepared. Polarizing microscopic textural observation shows that they are liquid crystals with nematic phase.     

The synthesis and mesomorphic properties of 4-n-alkoxyphenyl 4-[(4-n-alkoxy-2,3,5,6-tetrafluorophenyl)ethyl]benzoates

4-n-Alkoxyphenyl4-[(4-n-alkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]benzoates (compound A) are synthesised by a convenient method. These compounds exhibit only enantiotropic nematic phases and have very high clearing points. These compounds (As) can be transformed into corresponding ethane derivatives, via hydrogenation using a palladium catalyst (Pd/C), which exhibit monotropic nematic phases. The effect of the ethylene bridge (–CH₂CH₂–) on the mesomorphic behaviour is discussed.     

Synthesis and mesomorphic properties of n-butyl-4- [4-((4-n-alkoxyl-tetrafluorophenyl)ethynyl)benzyloxy]benzoates

A homologous series of n-butyl-4-[4-((4-n-alkoxyl-tetrafluorophenyl)ethynyl)benzyloxy]benzoates have been synthesized.Their phase transition temperatures have also measured by polarizing textural observation and confirmed by DSC.     

6-Hydroxyhexyl 4-(E)-4-alkoxy/halostyryl)benzoates: synthesis,characterisation and study of mesomorphic and fluorescent properties

Hydroxyhexyl esters of alkoxy and halostilbene carboxylic acids were prepared and studied for thermal, liquid crystalline and fluorescent properties. The decomposition temperatures were determined thermogravimetrically and the compounds were found stable at least up to 200°C. Differential scanning calorimetry (DSC) indicated two mesophases in alkoxystilbene caboxylates. The smectic nature of the liquid crystal (LC) compounds was identified from the optical textures and confirmed through X-ray diffraction (XRD) measurements, where SmA, SmB and CrE mesophases were observed. The compounds 3a-g and 3h-k show single absorption maxima in UV-visible spectra at around 338 and 322 nm, respectively. All the alkoxy compounds emit blue light in solution and in solid state in the wavelength range of 422–425 nm.     

Synthesis and mesomorphic properties of fluorinated phenyl 4‐[(4‐n‐alkoxy‐2,3‐difluorophenyl)ethynyl]benzoates

Three series of fluorinated phenyl 4‐[(4‐n‐alkoxy‐2,3‐difluorophenyl)ethynyl]benzoate liquid crystals have been synthesized. Their phase transition temperatures were measured by texture observation in a polarizing microscope and confirmed by DSC. Their mesomorphic properties and fluoro‐substituent effects were studied in detail.     

Synthesis and mesomorphic properties of 4-n-alkoxy 4'-[4-((4-n-alkoxy-2,3,5,6-tetrafluoro-phenyl)ethynyl)benzyloxy]benzoates

Two series of tolane-based liquid crystals have been prepared that incorporate a tetrafluorophenyl moiety and a flexible methyl ether bond into the core structure. The mesomorphic properties have been studied by polarizing microscopic textural observation and DSC measurements. By comparison with their non-fluorinated analogues, the effect of tetrafluorophenylene on mesomorphic behaviour has been discussed in this paper.     

Synthesis and mesomorphic properties of 3-(4-n-alkyloxyarylaminomethylene)chroman-2,4-diones

The synthesis, characterisation and mesomorphic properties of new liquid crystals are reported. The goal was to obtain amides starting from 7-decanoyloxychromone-3-carboxylic acid and 4-n-alkoxyanilines. However, instead of the expected amides, in each case a mixture of two isomeric E/Z enaminones was isolated, with a ratio 3/1. The mesophase behaviour of the five mixtures was characterised and studied using differential scanning calorimetry and polarising optical microscopy. The transitions are enantiotropic, the peaks being sharp and the mesomorphic range wide. All the compounds exhibit a smectic C phase and the derivatives with shorter chains also exhibit a nematic phase.