The twist bend nematic: a case of mistaken identity

@article{Samulski2020TheTB,
  title={The twist bend nematic: a case of mistaken identity},
  author={Edward T. Samulski and Alexandros G. Vanakaras and Demetri J. Photinos},
  journal={Liquid Crystals},
  year={2020},
  volume={47},
  pages={2092 - 2097}
}
ABSTRACT We review the physics underlying Meyer’s conjecture of how macroscopic-scale twist and bend conspire within the Frank-Oseen elasticity theory of nematics to create a heliconical arrangement of the uniaxial, apolar nematic director, the so-called ‘twist bend nematic’ NTB. We show that since 2011 a second, lower-temperature nematic phase observed in odd methylene-linked cyanobiphenyl dimers discovered by Toriumi and called NX, has been incorrectly identified as NTB. Moreover, as more… 
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TLDR
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Setting things straight in ‘The twist-bend nematic: a case of mistaken identity’
ABSTRACT Stimulated by the paper that precedes this, our aim is to correct an error made concerning the twist-bend nematic phase and to place its development, both theoretical and experimental, in
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References

SHOWING 1-10 OF 40 REFERENCES
Elastic continuum theory: towards understanding of the twist-bend nematic phases.
The twist-bend nematic phase, N_{TB}, may be viewed as a heliconical molecular arrangement in which the director n precesses uniformly about an extra director field, t. It corresponds to a nematic
Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised Maier-Saupe theory.
TLDR
Here, using a major extension of the Maier-Saupe molecular field theory, the transition from the nematic (N) to the NTB phase is described, and it is shown that on approaching the transition there is a gradual softening of the bend mode in the N phase.
A Liquid Crystalline Oligomer Exhibiting Nematic and Twist-Bend Nematic Mesophases.
  • R. Mandle, J. Goodby
  • Materials Science, Medicine
    Chemphyschem : a European journal of chemical physics and physical chemistry
  • 2016
TLDR
This Communication presents a study on T49, a liquid-crystalline oligomer exhibiting the twist-bend nematic phase, which has a molecular length that is of comparable dimensions to the sub-10 nm pitch determined for CB9CB, and provides new insights into the differentiation between the nano- and macro-science for self-assembling supermolecular systems.
A molecular theory of nematic-nematic phase transitions in mesogenic dimers.
TLDR
A simple molecular model that mimics the key features and symmetry (C2V) of this class of mesogens is presented and key experimental results on the NX phase of liquid crystalline dimers are discussed in the light of the theoretical predictions, which are also contrasted with the predictions of the twist-bend nematic model.
Nematic phase of achiral dimers spontaneously bends and twists
  • M. Čopič
  • Chemistry, Medicine
    Proceedings of the National Academy of Sciences
  • 2013
TLDR
Chen et al. (1) report on experiments that confirm the existence of a fourth nematic phase with some very interesting properties, which form the basis for the ubiquitous use of modern liquid-crystal displays.
Molecular dynamics simulations of nematic phases formed by cyano-biphenyl dimers
ABSTRACT Molecular dynamics simulations of selected members of the cyano-biphenyl (CB) series of dimers (CBnCB) have been set up using atomistic detail for the description of the alkyl spacer and
The chirality of a twist-bend nematic phase identified by NMR spectroscopy.
TLDR
The use of NMR spectroscopy is described to determine experimentally whether in reality the phase is chiral or not, and how the phase chirality can be demonstrated with probe molecules which contain deuteriated prochiral methylene groups.
Molecular shape as a means to control the incidence of the nanostructured twist bend phase.
TLDR
A computational study of the conformational landscape reveals the octam methyleneoxy spacer to have a broader distribution of bend-angles than the nonamethylene equivalent, leading to reductions in the thermal stability of the TB phase.
Nanoconfined heliconical structure of twist-bend nematic liquid crystal phase
ABSTRACT We produced controlled heliconical structures of a twist-bend nematic (NTB) liquid-crystal (LC) phase in nanoconfinement in a porous anodic aluminium oxide (AAO) film. The structural
Liquid crystals of the twenty-first century – nematic phase of bent-core molecules
Bent-core (BC) materials that form nematic liquid crystals (BC nematics (BCNs)) are known only since 2000, but since then they have been intensively studied. In this review we give a comprehensive
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