Zeinab Parsouzi
Pretransitional behavior of viscoelastic parameters at the nematic to twist-bend nematic phase transition in flexible: N -mers
Parsouzi, Zeinab; Babakhanova, Greta; Rajabi, Mojtaba; Saha, Rony; Gyawali, Prabesh; Turiv, Taras; Wang, Hao; Baldwin, Alan; Welch, Chris; Mehl, Georg H.; Gleeson, Jim T.; Jakli, Antal; Lavrentovich, Oleg D.; Sprunt, Samuel
Authors
Greta Babakhanova
Mojtaba Rajabi
Rony Saha
Prabesh Gyawali
Taras Turiv
Hao Wang
Alan Baldwin
Chris Welch
Professor Georg Mehl G.H.Mehl@hull.ac.uk
Professor of Organic and Materials Chemistry
Jim T. Gleeson
Antal Jakli
Oleg D. Lavrentovich
Samuel Sprunt
Abstract
© 2019 the Owner Societies. We report dynamic light scattering measurements of the orientational (Frank) elastic constants and associated viscosities among a homologous series of a liquid crystalline dimer, trimer, and tetramer exhibiting a uniaxial nematic (N) to twist-bend nematic (NTB) phase transition. The elastic constants for director splay (K11), twist (K22) and bend (K33) exhibit the relations K11 > K22 > K33 and K11/K22 > 2 over the bulk of the N phase. Their behavior near the N-NTB transition shows dependency on the parity of the number (n) of the rigid mesomorphic units in the flexible n-mers. Namely, the bend constant K33 in the dimer and tetramer turns upward and starts increasing close to the transition, following a monotonic decrease through most of the N phases. In contrast, K33 for the trimer flattens off just above the transition and shows no pretransitional enhancement. The twist constant K22 increases pretransitionally in both even and odd n-mers, but more weakly so in the trimer, while K11 increases steadily on cooling without evidence of pretransitional behavior in any n-mer. The viscosities associated with pure splay, twist-dominated twist-bend, and pure bend fluctuations in the N phase are comparable in magnitude to those of rod-like monomers. All three viscosities increase with decreasing temperature, but the bend viscosity in particular grows sharply near the N-NTB transition. The N-NTB pretransitional behavior is shown to be in qualitative agreement with the predictions of a coarse-grained theory, which models the NTB phase as a "pseudo-layered" structure with the symmetry (but not the mass density wave) of a smectic-A∗ phase.
Citation
Parsouzi, Z., Babakhanova, G., Rajabi, M., Saha, R., Gyawali, P., Turiv, T., …Sprunt, S. (2019). Pretransitional behavior of viscoelastic parameters at the nematic to twist-bend nematic phase transition in flexible: N -mers. Physical chemistry chemical physics : PCCP, 21(24), 13078-13089. https://doi.org/10.1039/c9cp00984a
Journal Article Type | Article |
---|---|
Acceptance Date | May 16, 2019 |
Online Publication Date | May 20, 2019 |
Publication Date | Jun 28, 2019 |
Deposit Date | Nov 30, 2020 |
Publicly Available Date | Jan 8, 2021 |
Journal | Physical Chemistry Chemical Physics |
Print ISSN | 1463-9076 |
Electronic ISSN | 1463-9084 |
Publisher | Royal Society of Chemistry |
Peer Reviewed | Peer Reviewed |
Volume | 21 |
Issue | 24 |
Pages | 13078-13089 |
DOI | https://doi.org/10.1039/c9cp00984a |
Public URL | https://hull-repository.worktribe.com/output/1865013 |
Additional Information | : This document is Similarity Check deposited; : Supplementary Information; : Single-blind; : Received 18 February 2019; Accepted 16 May 2019; Accepted Manuscript published 20 May 2019 |
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©2019 The authors. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder
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