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.

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