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Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer

Emsley, J. W.; Lelli, M.; Joy, H.; Tamba, M. G.; Mehl, G. H.

Authors

J. W. Emsley

M. Lelli

H. Joy

M. G. Tamba



Abstract

The order parameter, Szz, where z is the para axis of the difluoroterphenyl groups in DTC5C9, have been obtained from chemical shift anisotropies measured by ¹³C – {¹1H} NMR experiments at temperatures throughout the nematic, NU, and twist-bend nematic, NTB, phases shown by this compound. The order parameter temperature profiles are unusual in having a maximum value in the NU phase and then decreasing until the NTB phase is reached. There is a small discontinuity (~2%) in Szz at T_(NN_TB )and then a gradual decrease until a new phase appears. This behaviour is interpreted as revealing a temperature-dependent tilting of local directors in both phases away from the applied magnetic field direction. In the enantiomorphic twist-bend phase this tilt is consistent with the structure of the phase as a helical arrangement of local directors, whilst in the high-temperature non-chiral nematic the tilt must involve a non-chiral arrangement. It is proposed that in both phases the tilting of directors has a common origin in the bent shape of the molecules.

Citation

Emsley, J. W., Lelli, M., Joy, H., Tamba, M. G., & Mehl, G. H. (2016). Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer. Physical chemistry chemical physics : PCCP, 18(14), 9419-9430. https://doi.org/10.1039/c5cp07304a

Journal Article Type Article
Acceptance Date Mar 2, 2016
Online Publication Date Mar 16, 2016
Publication Date Apr 14, 2016
Deposit Date Mar 8, 2016
Publicly Available Date Mar 16, 2016
Journal Physical chemistry chemical physics
Print ISSN 1463-9076
Electronic ISSN 1463-9084
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 18
Issue 14
Pages 9419-9430
DOI https://doi.org/10.1039/c5cp07304a
Keywords Liquid cystal, Nematic, Twist-bend nematic, Order parameter, ¹³C NMR
Public URL https://hull-repository.worktribe.com/output/412487
Publisher URL http://pubs.rsc.org/en/Content/ArticleLanding/2016/CP/C5CP07304A#!divAbstract
Additional Information : This document is Similarity Check deposited; : Supplementary Information; : The PCCP Owner Societies have an exclusive publication licence for this journal; : Single-blind; : Received 26 November 2015; Accepted 2 March 2016; Advance Article published 16 March 2016; Version of Record published 30 March 2016
Contract Date Mar 8, 2016

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