Intercalated liquid-crystalline phases formed by symmetric dimers with an α,ω-diiminoalkylene spacer

Šepelj, Maja; Lesac, Andreja; Baumeister, Ute; Diele, Siegmar; Nguyen, Hai Duc; Bruce, Duncan W.

doi:10.1039/b612517d

Cited by 172 publications

(145 citation statements)

References 28 publications

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“…Analogous behavior is seen in dimers. For example, modification of CB7CB with alkoxy chain terminal, only dimers with short terminals (n=4) are able to form the N TB phase [23]. If the bent shape is lost altogether, for example in odd-numbered trimers, no N TB phase is observed [24].…”

Section: Discussionmentioning

confidence: 99%

Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen

et al. 2014

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The chiral, heliconical (twist-bend) nematic ground state is reported in an achiral, rigid, bent-core mesogen (UD68). Similar to the nematic twist-bend (N TB ) phase observed in bent molecular dimers, the N TB phase of UD68 forms macroscopic, smectic-like focal-conic textures and exhibits nanoscale, periodic modulation with no associated modulation of the electron density, i.e., without a detectable lamellar x-ray reflection peak. The N TB helical pitch is p TB ~ 14 nm. When an electric field is applied normal to the helix axis, a weak electroclinic effect is observed, revealing 50 µm -scale left-and right-handed domains in a chiral conglomerate.2

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Section: Discussionmentioning

confidence: 99%

Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen

et al. 2014

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“…The discovery of the twist-bend phase (N TB ) has given fresh impetus to the study of dimeric liquid crystals [1][2][3][4][5][6][7][8][9][10][11][12][13]. First predicted by Dozov [13], this liquid-crystalline state of matter has a locally helical structure with a pitch measured to be on the order of 10 nm [4,14], with this phase displaying a number of unusual and unique optical textures [15].…”

Section: Introductionmentioning

confidence: 99%

“…A number of reviews concerning the twist-bend phase have been published recently [18][19][20]. A relatively large number of dimeric liquid crystals are known to exhibit this state of matter [1,3,8,9,11,12,[21][22][23][24][25][26][27][28][29][30], and there is a growing number of liquid-crystalline oligomers known to exhibit the twist-bend phase [18,[31][32][33][34]. Additionally, this phase has been observed in a phenylpiperazine derived bent-core liquid crystal [4].…”

Section: Introductionmentioning

confidence: 99%

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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“…In recent years the new inhomogeneous nematic phases have been observed [1][2][3][4][5][6][7][8][9][10][11][12][13], and the study of the detailed structure of these phases is currently the most topical issue in liquid crystals research. The experiments for oligomers and bent-core systems indicate that there are at least two types of modulated nematic structures with one-dimensional periodicity.…”

Section: Introductionmentioning

confidence: 99%

Polar interactions between bent–core molecules as a stabilising factor for inhomogeneous nematic phases with spontaneous bend deformations

Osipov

Paja̧k

2016

Liquid Crystals

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This version is available at https://strathprints.strath.ac.uk/59161/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. It is generally accepted that the transition into the twist-bend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecular-statistical theory to show that sufficiently strong polar interactions between bent-shaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bent-core particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the one-particle distribution function.

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Intercalated liquid-crystalline phases formed by symmetric dimers with an α,ω-diiminoalkylene spacer

Cited by 172 publications

References 28 publications

Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen

Twist-bend heliconical chiral nematic liquid crystal phase of an achiral rigid bent-core mesogen

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

Polar interactions between bent–core molecules as a stabilising factor for inhomogeneous nematic phases with spontaneous bend deformations

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