Fine-tuning the effect of π–π interactions on the stability of the N<sub>TB</sub>phase

Knežević, Anamarija; Sapunar, Marin; Buljan, Anđela; Dokli, Irena; Hameršak, Zdenko; Kontrec, Darko; Lesac, Andreja

doi:10.1039/c8sm01569d

Cited by 32 publications

(25 citation statements)

References 44 publications

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“…[6][7][8] Other modulated nematic phases, possibly twist bend nematic variants, have also been reported. [9][10][11] Mertelj et al discovered a nematic phase with a periodically splayed local director, a splay nematic phase (NS, figure 1c), 12 which had been reported previously as a NX phase -i.e. a nematic phase of unknown structure.…”

Section: Introductionmentioning

confidence: 80%

Chemically induced splay nematic phase with micron scale periodicity

Connor

Mandle

2020

Soft Matter

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Section: Introductionmentioning

confidence: 80%

Chemically induced splay nematic phase with micron scale periodicity

Connor

Mandle

2020

Soft Matter

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“…We devised ether‐ and/or thioether‐linked 6‐(4‐cyanophenyl)‐2‐naphthyl‐ and 4‐cyanobiphenyl‐based dimers with heptylene spacers ( 1 – 7 ), and a series of homologues of dimer 3 [(CN)PNS n SNP(CN), where PN, (CN), and n denote a phenylnaphthyl ring core, cyano group, and odd number of carbon atoms in the alkyl spacer, respectively], as shown in Figure . We incorporated naphthalene as the π‐conjugated ring structure, since naphthalene‐containing dimers with methylene and other linkages exhibit the N TB phase . Their phase‐transition behaviors are discussed in terms of the chalcogen linkage type, mesogenic‐arm symmetry, and spacer length in detail.…”

Section: Introductionmentioning

confidence: 99%

“…We incorporated naphthalene as the p-conjugated ring structure, since naphthalene-containingd imers with methylene and other linkages exhibit the N TB phase. [60] Their phase-transition behaviors are discussed in terms of the chalcogen linkage type, mesogenic-arm symmetry,and spacer length in detail.…”

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 incidence of the N TB phase is intimately linked to molecular shape, specifically the bend angle between adjacent mesogenic units . The mesogenic units themselves are almost exclusively constructed from multiple benzene rings, and to date (as far as the authors are aware) the spacer is always appended to an aromatic ring rather than a saturated hydrocarbon; it is not clear if this is a consequence of synthetic convenience or a real structural requirement for materials to exhibit this phase of matter.…”

Section: Transition Temperatures (T °C) and Associated Enthalpies Omentioning

confidence: 99%

Utilising Saturated Hydrocarbon Isosteres of para Benzene in the Design of Twist‐Bend Nematic Liquid Crystals

Al-Janabi

Mandle

2020

ChemPhysChem

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The nematic twist-bend (N TB ) liquid crystal phase possesses a local helical structure with a pitch length of a few nanometres and is the first example of spontaneous symmetry breaking in a fluid system. All known examples of the N TB phase occur in materials whose constituent mesogenic units are aromatic hydrocarbons. It is not clear if this is due to synthetic convenience or a bona fide structural requirement for a material to exhibit this phase of matter. In this work we demonstrate that materials consisting largely of saturated hydrocarbons can also give rise to this mesophase.Furthermore, we find that replacement of 1,4-disubstituted benzene with trans 1,4-cyclohexane or 1,4-cubane does not especially alter the transition temperatures of the resulting material nor does it appear to impact upon the heliconical tilt angle. Each of these three units is effectively rigid and linear; calculating the probability distribution of bend angles for each compound reveals that the isosteric groups has little impact on the overall molecular shape, demonstrating the shape-driven nature of the N TB phase. Conversely, we find that incorporation of 2,6-disubstituted cuneane -a saturated hydrocarbon which is rigid but not linear -supresses the formation of the N TB phase.Liquid crystals are a collection of states of matter (mesophases) which possess orientational and/or positional order not found in the liquid state. Different LC mesophase are principally characterised by their degree of positional order; the nematic LC phase possesses long range orientational order, whereas smectic phases also exhibit positional order in one dimension. The discovery of nematic phases in which the average orientational order varies periodically -so called modulated nematics -has recently attracted significant interest. [1][2][3][4][5][6] The twist-bend nematic phase (N TB ) exhibits a heliconical precession of the nematic director through space with a periodic length scale of a few tens of nanometers. [7][8][9] This phase is typically found in materials comprising two or more mesogenic units which are mutually appended by a central spacer of such a length as to impart a gross bent shape. The incidence of the N TB phase is intimately linked to molecular shape, specifically the bend angle between adjacent mesogenic units. [10][11][12][13][14] The mesogenic units themselves are almost exclusively constructed from multiple benzene rings, and to date (as far as the authors are aware) the spacer is always appended to an aromatic ring rather than a saturated hydrocarbon; [15][16][17][18][19][20][21][22][23] it is not clear if this is a consequence of synthetic convenience or a real structural requirement for materials to exhibit this phase of matter.

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Fine-tuning the effect of π–π interactions on the stability of the N_TBphase

Abstract: The interplay between the molecular geometry and π–π interactions affects the thermal stability of a twist-bend nematic.

Cited by 32 publications

References 44 publications

Chemically induced splay nematic phase with micron scale periodicity

Chemically induced splay nematic phase with micron scale periodicity

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

Utilising Saturated Hydrocarbon Isosteres of para Benzene in the Design of Twist‐Bend Nematic Liquid Crystals

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Fine-tuning the effect of π–π interactions on the stability of the NTBphase

Abstract: The interplay between the molecular geometry and π–π interactions affects the thermal stability of a twist-bend nematic.

Cited by 32 publications

References 44 publications

Chemically induced splay nematic phase with micron scale periodicity

Chemically induced splay nematic phase with micron scale periodicity

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

Utilising Saturated Hydrocarbon Isosteres of para Benzene in the Design of Twist‐Bend Nematic Liquid Crystals

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Fine-tuning the effect of π–π interactions on the stability of the N_TBphase