Geometric aspects influencing N-N<sub>TB</sub>transition - implication of intramolecular torsion

Lesac, Andreja; Baumeister, Ute; Dokli, Irena; Hameršak, Zdenko; Ivšić, Trpimir; Kontrec, Darko; Viskić, Marko; Knežević, Anamarija; Mandle, Richard J.

doi:10.1080/02678292.2018.1453556

Cited by 42 publications

(29 citation statements)

References 46 publications

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“…16 This phase is principally exhibited by liquid-crystalline dimers, 17 in which two rigid sections are adjoined by a (semi) flexible spacer. Experimental results suggest it is primarily molecular shape [18][19][20] and the gross bend-angle that appear to dictate the incidence of this phase, [20][21][22] supporting the findings of earlier theoretical treatments. 23,24 In addition to low molecular weight dimers the TB phase is also found in oligomers, [25][26][27][28] polymers 29,30 and possibly lyotropic systems.…”

Section: Introductionsupporting

confidence: 68%

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

Mandle

Jw²

2018

Preprint

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From the observation of a previously undiscovered nematic-like mesophase (N X ) by Archbold et al, we report on several new binary liquid-crystalline mixtures between the high helical twisting power dopant RM1041 and a selection of dimers with varying average bend angles and conformational landscapes. We also report on mixtures between RM1041 and oligomeric LC materials. We find that dimers and oligomers exhibit not only chiral nematic and twist-bend modulated phases, but also the same N X phase reported by Archbold, indicating that this state of matter (the structure of which is yet to be definitively characterised) is exhibited by a wide range of materials. Mixtures of the dimer CB9CB with a selection of different chiral dopants suggest that it is the helical twisting power of the chiral additive that is responsible incidence of the N X phase.

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Section: Introductionsupporting

confidence: 68%

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

Mandle

Jw²

2018

Preprint

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“…Thus far,anumber of twist-bend nematicd imers with variousb ond linkages (e.g., ketone, ester,and imine)h ave been developed with exclusively carbon or oxygen atoms located at the linkagep ositions. [44][45][46][47][48] Mandle et al systematicallyv alidated that am ajority of dimers with N TB phases have a < 1308. [44] Although the a value of a single conformer with an all-trans alkyl spaceri su seful for designing new twist-bend nematic dimers, in actuality ac onformationald istribution with "average molecular bend angle" occursd ue to the gauche conformation and flexibility.T he former a value is apt to be overestimated from the latter average molecular benda ngle.…”

Section: Introductionmentioning

confidence: 99%

Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase

Arakawa

Ishida

Tsuji

2020

Chemistry A European J

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The twist–bend nematic (NTB) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent‐shaped molecules is a hot topic of current liquid‐crystal science. As opposed to the most common methylene‐linked dimers, this study demonstrates chalcogen ether‐ and/or thioether‐linked 6‐(4‐cyanophenyl)‐2‐naphthyl‐based liquid‐crystal dimers with symmetric and asymmetric π‐conjugated mesogenic‐arm structures that exhibit the NTB phase. Although the symmetric bis(ether)‐linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)‐linked dimer can form the NTB phase. All thioether‐linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic‐arm symmetry, and spacer length. It is revealed that thioether‐linked dimers based on asymmetric π‐conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature.

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“…The twist-bend modulated nematicp hase (TB), the averageo rientation of the nematic phase rotateso ver af ew nanometers giving ah elical structure with ar emarkably short pitch length. [20] Experimental resultss uggest it is primarily molecular shape [14,21,22] and the gross bend-angle whicha ppeart odictatet he incidenceo ft his phase, [14,23,24] supporting the findings of earliert heoretical treatments. [10][11][12] Although this phase is principally exhibited by liquid-crystalline dimers, in which two rigid sections are adjoined by a( semi-) flexible spacer, [13,14] it has also been observed in semi-rigid bent-core materials, [15] liquid crystalline nmers [16][17][18][19] and polymers.…”

Section: Introductionmentioning

confidence: 54%

“…[1][2][3] Different LC mesophase are principally characterised by their degree of orientational and/orp ositional order;f or example, the nematic LC phase possesses long range orientational order with short range positional order,w hereasl amellar phases also exhibit positional order in one dimension. [10][11][12] Although this phase is principally exhibited by liquid-crystalline dimers, in which two rigid sections are adjoined by a( semi-) flexible spacer, [13,14] it has also been observed in semi-rigid bent-core materials, [15] liquid crystalline nmers [16][17][18][19] and polymers. [4][5][6][7][8][9] The N TB phase is therefore chiral despite being typicallyf ormed by achiralm olecules, although ah andfulo fc hiral materials are also known to exhibit this phase.…”

Section: Introductionmentioning

confidence: 99%

Molecular Flexibility and Bend in Semi‐Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State

Mandle

Goodby

2019

Chemistry A European J

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The N TB phase phases possess al ocal helicals tructure with ap itch length of af ew nanometers and is typically exhibited by materials consisting of two rigid mesogenic units linked by af lexible oligomethylene spacer of odd parity,g iving ab ent shape. We report the synthesis and characterisation of two novel dimeric liquid crystals, and perform ac omputational study on 10 cyanobiphenyl dimers with varying linking groups, generating al arge libraryo f conformers for each compound;t his allows us to present molecular bend angles as probability weighted averages of many conformers, rather than use as ingle conformer.W e validate conformer libraries by comparison of interproton distances with those obtained from solution-based 1D 1 H NOESYN MR, finding good agreement between experiment and computational work. Conversely,w ef ind that using any singlec onformer fails to reproduce experimental interproton distances. We find the use of as ingle conformers ignificantly overestimatest he molecular bend angle while also ignoring flexibility;i na ddition,w es how that the average bend angle and flexibility are both linkedt ot he relative stabilityo ft he N TB phase. Experimental SectionCompound 1 has been extensively studied, [32] compounds 2-5 were reported in ref.[24],c ompounds 6, 7 and 8 were reported by Arakawa et al. in ref.[27] and [28].C ompounds 9 and 10 were synthesised as part of this work accordingt oS cheme 1. Steglich [a] R.

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Geometric aspects influencing N-N_TBtransition - implication of intramolecular torsion

Cited by 42 publications

References 46 publications

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase

Molecular Flexibility and Bend in Semi‐Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State

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Geometric aspects influencing N-NTBtransition - implication of intramolecular torsion

Cited by 42 publications

References 46 publications

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

A Novel Nematic-Like Mesophase Induced in Dimers, Trimers and Tetramers Doped with a Highly Chiral Additive

Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase

Molecular Flexibility and Bend in Semi‐Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State

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Geometric aspects influencing N-N_TBtransition - implication of intramolecular torsion