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Article

The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures

1
Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
2
School of Electronic & Electrical Engineering, Sungkyunkwan University, Suwon 440-746, Korea
3
Department of Chemistry, University of Hull, Hull HU6 7RX, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Charles Rosenblatt
Crystals 2021, 11(6), 621; https://doi.org/10.3390/cryst11060621
Received: 29 April 2021 / Revised: 20 May 2021 / Accepted: 25 May 2021 / Published: 31 May 2021
(This article belongs to the Special Issue In Celebration of Noel A. Clark’s 80th Birthday)
The twist-bend nematic phase (NTB) exhibits a complicated hierarchy of structures responsible for several intriguing properties presented here. These are: the observation of a fast electrooptic response, the exhibition of a large electroclinic effect, and the observation of an unusual pattern of the temperature dependence of birefringence of bent-shaped bimesogens in parallel-rubbed planar-aligned cells. These unusual effects inspired the use of highly sophisticated techniques that led to the discovery of the twist-bend nematic phase. Results of the optical retardation of a parallel-rubbed planar-aligned cell show that the ‘heliconical angle’ (the angle the local director makes with the optical axis) starts increasing in the high temperature N phase, it exhibits a jump at the N–NTB transition temperature and continues to increase in magnitude with a further reduction in temperature. The liquid crystalline parallel-rubbed planar-aligned and twist-aligned cells in this phase exhibit fascinating phenomena such as a demonstration of the beautiful stripes and dependence of their periodicity on temperature. The Fréedericksz transition in the NTB phase is found to be of the first order both in rubbed planar and homeotropic-aligned cells, in contrast to the second order transition exhibited by a conventional nematic phase. This transition shows a significant hysteresis as well as an abrupt change in the orientation of the director as a function of the applied electric field. Hierarchical structures are revealed using the technique of polymer templating the structure of the liquid crystalline phase of interest, and imaging of the resulting structure by scanning electron microscopy. View Full-Text
Keywords: twist-bend nematic phase; nematic liquid crystals; stripe textures; Fréedericksz transition; optical retardation; birefringence twist-bend nematic phase; nematic liquid crystals; stripe textures; Fréedericksz transition; optical retardation; birefringence
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MDPI and ACS Style

Panov, V.P.; Song, J.-K.; Mehl, G.H.; Vij, J.K. The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures. Crystals 2021, 11, 621. https://doi.org/10.3390/cryst11060621

AMA Style

Panov VP, Song J-K, Mehl GH, Vij JK. The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures. Crystals. 2021; 11(6):621. https://doi.org/10.3390/cryst11060621

Chicago/Turabian Style

Panov, Vitaly P., Jang-Kun Song, Georg H. Mehl, and Jagdish K. Vij 2021. "The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures" Crystals 11, no. 6: 621. https://doi.org/10.3390/cryst11060621

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