Issue 9, 2020

Study of ferro- and anti-ferroelectric polar order in mesophases exhibited by bent-core mesogens

Abstract

The polar nature of three pure homologous bent-core compounds derived from 4-cyanoresorcinol bisbenzoates as a central core unit were studied based on dielectric spectroscopy measurements and electro-optical investigation. All these compounds exhibited a highly correlated nematic phase (NCybC) followed by a phase (CybC) comprising elongated but not completely fused strings of cybotactic clusters. Additionally, the higher homologous compounds exhibited one or more tilted smectic phases (SmC(I), SmC(II)). Based on all the investigated results, the NCybC phase was found to be quite different from the usual nematics, consisting of tiny polar clusters, which in effect revealed a ferroelectric polarization within the medium. Moreover, the lower temperature SmC phases (SmC(I) and SmC(II)) characterized an anti-ferroelectric type of molecular dipolar ordering in adjacent layers. The intermediate CybC phase accomplished the transition from the ferroelectric-type NCybC phase to the anti-ferroelectric type of the SmC(I) phase, where the cybotactic clusters were elongated. The SmC(II) phase was a SmC phase with an enhanced packing density in comparison to the SmC(I) phase, which seems like a more solid-like state or glassy state. The field reversal polarization technique and the simultaneous observation of the optical textures corroborated the polar nature of the mesophases. These outcomes were explained by considering the structural changes of the molecules by increasing the chain length and the combined effect of their association in the dielectric parameters of the respective mesophases. Finally, it was concluded that the SmC(I) phase should be designated as SmCsPA phase (Cs stands for a synclinic-type of molecular organization and PA corresponds to an anti-ferroelectric ordering of the polar orientation in neighboring layers), where the SmC(II) phase was characterized by a quite solid-like state or close-packed SmC phase with a similar type of synclinic anti-ferroelectric ordering (SmCsPA phase).

Graphical abstract: Study of ferro- and anti-ferroelectric polar order in mesophases exhibited by bent-core mesogens

Supplementary files

Article information

Article type
Paper
Submitted
04 Sept. 2020
Accepted
01 Nov. 2020
First published
03 Nov. 2020
This article is Open Access
Creative Commons BY-NC license

Mater. Adv., 2020,1, 3545-3555

Study of ferro- and anti-ferroelectric polar order in mesophases exhibited by bent-core mesogens

S. Chakraborty, M. Kumar Das, C. Keith and C. Tschierske, Mater. Adv., 2020, 1, 3545 DOI: 10.1039/D0MA00678E

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements