Please use this identifier to cite or link to this item:
http://hdl.handle.net/2289/7287
Title: | Simple model for the stripe phase in compounds with bent-core molecules which exhibit a lower-temperature ferroelectric smectic-A phase |
Authors: | Madhusudana, N.V. |
Issue Date: | Aug-2019 |
Publisher: | American Physical Society |
Citation: | Physical Review E, 2018, Vol.100, p022706 |
Abstract: | Bent-core (BC) molecules usually exhibit polar packing in smectic layers in which the long or bow axes tilt with respect to the layer normal. In many compounds, the tilt angle goes to zero, and typically the polarization(P) of neighboring layers has an antiferroelectric order (SmAPAF). A careful molecular engineering has led to the discovery of the ferroelectric SmAPF phase in a few BC compounds. Detailed experimental studies [Zhu et al., J. Am. Chem. Soc. 134, 9681 (2012)] have shown that one of the compounds undergoes a weak first order transition to a striped phase (SmAPFmod ), in which the repolarization switching occurs at a threshold electric field, the latter increasing with temperature. The main optical birefringence of the SmAPFmod phase increases rapidly with the field at lower temperatures of its range. A small (<10%) fraction of the BC molecules can be expected to have less bent conformations in excited states (ESs), and we argue that the ES conformers rotate freely about the bow axes, and aggregate to form regions without any polar order to gain rotational entropy. In turn, a favorable divP term leads to the formation of stripes in the polarized regions made of ground state conformers. Based on this physical picture, we develop a simple phenomenological model to reproduce all the experimental trends qualitatively. In sample cells with insulating layers neighboring stripes prefer to have an antiparallel orientation of the mean P direction. The dielectric constant of the stripe phase increases with a dc bias electric field, a trend which is opposite to that in other ferroelectric liquid crystals. |
Description: | Open Access |
URI: | http://hdl.handle.net/2289/7287 |
ISSN: | 2470-0045 2470-0053 (Online) |
Alternative Location: | https://doi.org/10.1103/PhysRevE.100.022706 |
Copyright: | 2019 American Physical Society |
Appears in Collections: | Research Papers (SCM) |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
2019_PhysRevE_Vol.100_p022706.pdf | Open Access | 682.29 kB | Adobe PDF | View/Open |
Items in RRI Digital Repository are protected by copyright, with all rights reserved, unless otherwise indicated.