Spontaneous formation of chiral macrostructures in achiral hockey-stick liquid crystals

Belaissaoui, Abdelhak; Cowling, Stephen J.; Goodby, John W.

doi:10.1080/02678292.2013.780268

Cited by 21 publications

(18 citation statements)

References 23 publications

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“…The unusual dielectric relaxation behaviour that can be seen in bent‐core nematic systems, mentioned in Section 3.3, leads us to expect that the electro‐optic responses of such systems could be very different from those in calamitic systems. Further, spontaneous chirality in bent‐core nematic materials is well documented,11–13, 45, 52 and has also been observed recently in hockey‐stick‐shaped oxadiazole‐based materials 53. Again, the spontaneous chirality could potentially influence some of the electro‐optic behaviour.…”

Section: Electric‐field Phenomenamentioning

confidence: 65%

The Nematic Phases of Bent‐Core Liquid Crystals

et al. 2014

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Over the last ten years, the nematic phases of liquid crystals formed from bent-core structures have provoked considerable research because of their remarkable properties. This Minireview summarises some recent measurements of the physical properties of these systems, as well as describing some new data. We concentrate on oxadiazole-based materials as exemplars of this class of nematogens, but also describe some other bent-core systems. The influence of molecular structure on the stability of the nematic phase is described, together with progress in reducing the nematic transition temperatures by modifications to the molecular structure. The physical properties of bent-core nematic materials have proven difficult to study, but patterns are emerging regarding their optical and dielectric properties. Recent breakthroughs in understanding the elastic and flexoelectric behaviour are summarised. Finally, some exemplars of unusual electric field behaviour are described.

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Section: Electric‐field Phenomenamentioning

confidence: 65%

The Nematic Phases of Bent‐Core Liquid Crystals

et al. 2014

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“…As additional proof, smectic layers within a nematic phase of a BCM have been imaged using cryo-transmission electron microscopy. [25] The cluster model has also been used to explain some other interesting features of BCM, such as the fact that chiral domains are observed when the sample is viewed by polarising microscopy (POM), [26][27][28][29][30][31][32] and ferroelectric switching behaviour in the nematic phase of 1,2,4-oxadiazolebased liquid crystals. [33][34][35][36][37] However, some differences of opinion regarding the precise cause of the observed behaviour in the nematic phase remain.…”

Section: Introductionmentioning

confidence: 99%

The effects of lateral halogen substituents on the low-temperature cybotactic nematic phase in oxadiazole based bent-core liquid crystals

et al. 2015

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Scharrer (2015): The effects of lateral halogen substituents on the low-temperature cybotactic nematic phase in oxadiazole based bent-core liquid crystals, Liquid Crystals,We have previously demonstrated that the incorporation of lateral methyl groups on oxadiazole-based liquid crystals leads to relatively low-temperature cybotactic nematic phases which, in some cases, supercool to room temperature. We report here the synthesis and phase behaviour of related compounds that possess lateral halogen groups and in some cases, lateral methyl groups as well. Derivatives with three lateral substituents (one halogen and two methyl groups) in a specific pattern supercool in the nematic phase to room temperature. As was the case with the previously reported trimethylated derivatives, the low-temperature nematic phase is glassy in nature. Two of the new trisubstituted derivatives (with bromo and chloro groups) remain in the nematic phase upon subsequent heating until transitioning to the isotropic phase indicating that the low-temperature nematic phase may be more stable than that shown by the trimethylated analogue. Preliminary X-ray diffraction analysis confirms the presence of a tilted cybotactic nematic phase. In addition, the splitting observed in the wide-angle scattering feature is indicative of enhanced local biaxial packing.

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“…M 3-((4-(Benzyloxy)benzoyl)oxy)phenyl-4-(n-decyloxy)benzoate (11) This compound was prepared by the esterification of compound 10 with 4-benzoyloxybenzoic acid using DCC coupling method described earlier. [26] The analytical data obtained are as follows:…”

Section: -Hydroxyphenyl-4-(n-decyloxy)benzoate (10)mentioning

confidence: 99%

“…Here, the two arms differ to a great extent with regard to their lengths. [1][2][3][4][5][6][7][8][9][10][11] Generally, the hockey stick mesogens exhibit smectic and nematic mesophases. Interestingly, in some of the cases, the occurrence of two polymorphic tilted smectic phases i.e., SmC s and SmC a , are observed.…”

Section: Introductionmentioning

confidence: 99%

Hockey stick-shaped azo compounds: effect of linkage groups and their direction of linking on mesomorphic properties

2015

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Several new hockey stick-shaped azo compounds are designed and synthesised with an aim to study the effect of different types of linkages and their direction of linking on the mesomorphic properties in such systems. The new compounds synthesised are characterised by spectroscopic methods. The liquid crystalline properties are investigated using polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. They exhibited a variety of mesophases such as nematic (N), smectic A (SmA), anticlinic smectic C (SmC a ), B 1 , etc. We found that the direction of linkage groups has a major effect on the mesomorphic properties when compared to the effect of different types of linkage groups. We observed a reversible photoswitching phenomenon of these compounds in their solution UV-vis spectra.

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Spontaneous formation of chiral macrostructures in achiral hockey-stick liquid crystals

Cited by 21 publications

References 23 publications

The Nematic Phases of Bent‐Core Liquid Crystals

The Nematic Phases of Bent‐Core Liquid Crystals

The effects of lateral halogen substituents on the low-temperature cybotactic nematic phase in oxadiazole based bent-core liquid crystals

Hockey stick-shaped azo compounds: effect of linkage groups and their direction of linking on mesomorphic properties

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