Search for biaxiality in a shape-persistent bent-core nematic liquid crystal

Kim, Young-Ki; Majumdar, Madhabi; Senyuk, Bohdan; Tortora, Luana; Seltmann, Jens; Lehmann, Matthias; Jákli, Antal; Gleeson, J. T.; Lavrentovich, Oleg D.; Sprunt, Samuel

doi:10.1039/c2sm26278a

Cited by 56 publications

(44 citation statements)

References 53 publications

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“…[38][39][40][41] Clearly, there continues to be much to learn about the fundamentals of how the bent-core molecules are interacting to establish supramolecular structures in the nematic phase and this is being investigated using a variety of techniques. [42][43][44][45][46][47][48][49] Moreover, several recent studies suggest that fast electro-optical switching about the minor director of a BCM in a field-induced N b phase is possible, so continued investigations into this unique liquid crystal phase hold technological promise. [50][51][52] One of the challenges in studying these types of compounds is that most of the derivatives that show the unique N Cyb phase do so at very high temperatures.…”

Section: Introductionmentioning

confidence: 98%

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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Section: Introductionmentioning

confidence: 98%

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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“…(46,47) are those introduced by Gramsbergen et al [1], and facilitate comparison with previous work.…”

Section: B Free Energymentioning

confidence: 99%

“…This study provides extra indirect calorimetric evidence of the biaxiality of the bent-core molecules used in the experiments of Ostapenko et al [6], for both our work and that of others [18,19] also predict reduced values of T N I − T bf . In addition, other techniques provide more direct evidence of these biaxial effects [46]. The background to the experimental studies is that it has turned out to be very difficult to persuade nematogens to exhibit a magnetic-field-dependent transition [2,3], and that when it was observed it was extremely weak.…”

Section: A Comparison With Experimentsmentioning

confidence: 99%

Biaxiality-induced magnetic field effects in bent-core nematics: Molecular-field and Landau theory

Sluckin

Luckhurst

2013

Phys. Rev. E

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Nematic liquid crystals composed of bent-core molecules exhibit unusual properties, including an enhanced Cotton-Mouton effect and an increasing isotropic (paranematic)-nematic phase transition temperature as a function of magnetic field. These systems are thought to be good candidate biaxial liquid crystals. Prompted by these experiments, we investigate theoretically the effect of molecular biaxiality on magnetic field-induced phenomena for nematic liquid crystals, using both molecular field and Landau theory. The geometric mean approximation is used in order to specify the degree of molecular biaxiality using a single parameter. We reproduce experimental field-induced phenomena, and predict also an experimentally accessible magnetic critical point. The Cotton-Mouton effect and temperature dependence of the paranematic-nematic phase transition are more pronounced with increased molecular biaxiality. We compare our theoretical approaches and make contact with recent relevant experimental results on bent-core molecular systems.

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“…After injection, the 5CB was quenched into the nematic phase. The temperature was subsequently held constant to prevent flow due to thermal-expansion of 5CB [31][32][33]. In this geometry, n escapes in the direction of the capillary axis, leading to point singularities at domain boundaries [1,3].…”

mentioning

confidence: 99%

Experimental Insights into the Nanostructure of the Cores of Topological Defects in Liquid Crystals

et al. 2016

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Search for biaxiality in a shape-persistent bent-core nematic liquid crystal

Cited by 56 publications

References 53 publications

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

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

Biaxiality-induced magnetic field effects in bent-core nematics: Molecular-field and Landau theory

Experimental Insights into the Nanostructure of the Cores of Topological Defects in Liquid Crystals

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