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Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism

Stevenson, Warren D.; Zeng, Xiangbing; Welch, Chris; Thakur, Anil K.; Ungar, Goran; Mehl, Georg H.

Authors

Warren D. Stevenson

Xiangbing Zeng

Chris Welch

Anil K. Thakur

Goran Ungar



Abstract

Many achiral bent molecules and some polymers with such repeat units exhibit a liquid crystal phase transition between a conventional nematic (N), and a second nematic (Nx) with periodically modulated orientation. Theory predicts several possible structures for the Nx phase, some of which are chiral (helical), and others achiral (e.g. zigzag). Experimentally distinguishing which modulation type is present is non-trivial and the structure is often assumed to be helical despite the other possibilities. Here we use circular dichroism (CD) spectroscopy to directly and unambiguously identify chirality in the Nx phase of two different dimer series, “DTC5Cn” and “CBCnCB”, which vary in (CH2)n spacer length (n=5, 7, 9). In doing so we have determined that the modulation type is helical in all samples. The temperature dependence of the CD signal was also investigated, suggesting that the helical structure progressively unwinds on approach to the high temperature N phase

Citation

Stevenson, W. D., Zeng, X., Welch, C., Thakur, A. K., Ungar, G., & Mehl, G. H. (2020). Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism. Journal of materials chemistry. C, 8, 1041-1047. https://doi.org/10.1039/c9tc05061b

Journal Article Type Article
Acceptance Date Dec 3, 2019
Online Publication Date Dec 6, 2019
Publication Date 2020
Deposit Date Feb 18, 2020
Publicly Available Date Nov 30, -0001
Journal Journal of Materials Chemistry C
Print ISSN 2050-7526
Electronic ISSN 2050-7534
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 8
Pages 1041-1047
DOI https://doi.org/10.1039/c9tc05061b
Keywords Materials Chemistry; General Chemistry
Public URL https://hull-repository.worktribe.com/output/3323595
Additional Information : This document is Similarity Check deposited; : Supplementary Information; : Xiangbing Zeng (ORCID); : Chris Welch (ORCID); : Goran Ungar (ORCID); : Georg H. Mehl (ORCID); : Single-blind; : Received 13 September 2019; Accepted 3 December 2019; Accepted Manuscript published 6 December 2019; Advance Article published 12 December 2019