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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.

Journal Article Type Article
Publication Date Apr 14, 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
APA6 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
DOI https://doi.org/10.1039/c5cp07304a
Keywords Liquid cystal, Nematic, Twist-bend nematic, Order parameter, ¹³C NMR
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

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