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

TY - JOUR

T1 - Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

AU - Archbold, Craig Thomas

AU - Mandle, Richard

AU - Andrews, Jessica L.

AU - Cowling, Stephen James

AU - Goodby, John William

N1 - © 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

PY - 2017/8/2

Y1 - 2017/8/2

N2 - 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.

AB - 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.

U2 - 10.1080/02678292.2017.1360954

DO - 10.1080/02678292.2017.1360954

M3 - Article

SN - 0267-8292

SP - 1

EP - 11

JO - LIQUID CRYSTALS

JF - LIQUID CRYSTALS

ER -