Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

Paterson, Daniel A.; Abberley, Jordan P.; Harrison, William T.; Storey, John M. D.; Imrie, Corrie T.

doi:10.1080/02678292.2016.1274293

Cited by 92 publications

(128 citation statements)

References 61 publications

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“…We therefore constructed a phase diagram for binary mixtures of compound 7/CB9CB; a plot of T N TB ÀN versus concentration was constructed; whereas there is typically a linear relationship between concentration and transition temperature, we observed stabilisation of the N TB phase in mixtures, as was observed much earlier by Ramou et al [43]. An acceptable fit to the data was obtained using a quadratic function (R 2 > 0.95), and from this, we obtained a transition temperature value of 82°C (phase diagram and equation in ESI), in good agreement with Paterson et al [42]. As reported by us previously the diketone-…”

Section: Resultssupporting

confidence: 74%

“…Similarly, replacement of the methylene linking unit of 6 with an alkyne to afford 5 yields an increase in melting point and reductions in the clearing point (~8°C) and N-N TB transition temperature (~22°C). It has recently been reported that 7 (CBO5OCB) exhibits the twist-bend phase upon deep supercooling to~78°C [42]. We were able to observe what we believe to be the N TB phase by ejecting the sample into liquid nitrogen (i.e.…”

Section: Resultssupporting

confidence: 49%

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Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

et al. 2017

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The twist-bend phase (N TB ) is most commonly observed in materials with a gross-bent shape: dimers; bent-cores; bent-oligomers. We had suggested previously that the bend-angle of such systems effectively dictates the relative thermal stability of the N TB phase. However, our earlier paper relied on the use of a single energy-minimum conformer and so failed to capture any information about flexibility and conformational distribution. In the present work, we revisit our hypothesis and examine a second set of dimers with varying linking groups and spacer composition. We have improved on our earlier work by studying the conformational landscape of each material, allowing average bend-angles to be determined as well as the conformer distribution. We observe that the stability of the N TB phase exhibits a strong dependence not only on the Boltzmann-weighted average bend-angle (rather than just a static conformer), but also on the distribution of conformers. To a lesser extent, the flexibility of the spacer appears important. Ultimately, this work satisfies both theoretical treatments and our initial experimental study and demonstrates the importance of molecular bend to the N TB phase. ARTICLE HISTORY

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Section: Resultssupporting

confidence: 74%

Section: Resultssupporting

confidence: 49%

Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

et al. 2017

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“…The data was taken from refs. [10,11,20,[22][23][24][25][26][27][28], and recent publications also support this analysis [29][30][31][32][33].…”

Section: −1supporting

confidence: 57%

Free volume, molecular grains, self-organisation, and anisotropic entropy: machining materials

Goodby

2017

Liquid Crystals

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“…It is known that the bend-angle dictates the incidence of the twist-bend nematic phase; this is demonstrated by comparing CB9CB (which exhibits the N TB phase) to the bis ether-linked CBO7OCB (which does not). The material CB8OCB (Figure 9) is 'halfway' between these two materials, having one methylene-and one ether-linking group, and this also exhibits the N TB phase, having been reported by us previously [40] and more recently by others [21]. It has been observed that as the number of ether linkages increases, the scaled N TB transition temperature (T NTB-N /T N-Iso ) decreases irrespective of the actual values of T NTB-N .…”

Section: Resultsmentioning

confidence: 98%

“…It has been observed that many functional groups -including the SF 5 groupcan be incorporated into the structure of a suitable dimer without loss of the N TB phase. Last, the twistbend nematic phase -in dimers and bimesogens at least -is found mostly for methylene-linked materials, although a number of other linking groups are known to yield materials that afford this mesophase [7,21,22,33,[44][45][46][47][48][49]. In the first part of this paper, we present the latest part of our study into the structureproperty relationships of bis ether-linked dimers and bimesogens that exhibit the twist-bend phase.…”

Section: Introductionmentioning

confidence: 99%

Developments in liquid-crystalline dimers and oligomers

2017

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Liquid-crystalline dimers and bimesogens have attracted much attention due to their propensity to exhibit the spontaneously chiral twist-bend mesophase (N TB ), most often by dimers with methylene spacers. Despite their relative ease of synthesis, the number of ether-linked twistbend materials significantly lags behind those of methylene-linked compounds. In this work, we have prepared and studied a range of ether-linked bimesogens homologous in structure to the FFO9OCB; as with methylene-linked systems, it appears that it is molecular topology and the gross molecular shape that are the primary drivers for the formation of this phase of matter. Dimers and bimesogens are well studied within the context of the twist-bend phase; however, present understanding of this mesophase in oligomeric systems lags far behind. We report our recent efforts to prepare further examples of oligomeric twist-bend nematogens, including further examples of our 'n+1' methodology, which may allow the synthesis of high-purity, monodisperse materials of any given length to be prepared. We have observed that there is a tendency for these materials to exhibit highly ordered soft-crystalline mesophases as opposed to the twist-bend phase.ARTICLE HISTORY

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Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

Cited by 92 publications

References 61 publications

Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

Free volume, molecular grains, self-organisation, and anisotropic entropy: machining materials

Developments in liquid-crystalline dimers and oligomers

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