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Invited Article

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

, ORCID Icon, , ORCID Icon &
Pages 2079-2088 | Received 08 Jun 2017, Published online: 02 Aug 2017
 

ABSTRACT

The twist-bend phase (NTB) 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 NTB 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 NTB 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 NTB phase.

Graphical Abstract

Acknowledgements

CTA thanks the University of York for the award of a doctoral scholarship. The EPSRC is thanked for funding the Bruker D8 small-angle X-ray scattering instrument used in this work via grant EP/K039660/1.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Engineering and Physical Sciences Research Council: [grant EP/K039660/1].