Optical Microscopy Observations and Construction of Dupin Cyclides at the Isotropic/Smectic A Phase Transition.

Mikhael Halaby Macary,Valentin Dubuffet,Antoine Gibek,Justin Picart,Roll Freddy Dimeni,Benoît Dupuy,Gauthier Damême,Claire Meyer

doi:10.3390/ma14164539

Mikhael Halaby Macary, Valentin Dubuffet + Show 6 more

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https://doi.org/10.3390/ma14164539

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Journal: Materials	Publication Date: Aug 12, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: University of Picardie Jules Verne

Abstract

In this work, we are interested in the nucleation of bâtonnets at the Isotropic/Smectic A phase transition of 10CB liquid crystal. Very often, these bâtonnets are decorated with a large number of focal conics. We present here an example of a bâtonnet obtained by optical crossed polarized microscopy in a frequently observed particular area of the sample. This bâtonnet presents bulges and one of them consists of a tessellation of ellipses. These ellipses are two by two tangent, one to each other, and their confocal hyperbolas merge at the apex of the bâtonnet. We propose a numerical simulation with Python software to reproduce this tiling of ellipses as well as the shape of the smectic layers taking the well-known shape of Dupin cyclides within this particular bâtonnet area.

Highlights

Thermotropic Liquid Crystals (LCs) are intermediate phases between crystalline solids and isotropic liquids, and they can be made of elongated molecules—called “mesogens”—which in turn possess a rigid core consisting of a set of phenyl groups and flexible tails of varying lengths consisting of alkyl terminal chains R and R’ as shown in Figure 1a for instance
What is interesting in this work is that a part of the smectic phase appears in the form of “bâtonnets” (Figure 4a,b)
The bâtonnets rotate quickly and, in order to stabilize the texture observed in Figure 4a, the temperature has been very slowly increased

Summary

Introduction

—which in turn possess a rigid core consisting of a set of phenyl groups and flexible tails of varying lengths consisting of alkyl terminal chains R and R’ as shown in Figure 1a for instance. They exhibit a very rich polymorphism—or mesomorph phases—depending on temperature: nematics, smectics A, B, C, E, etc. In a Smectic A phase (Figure 1b), the mesogens are arranged in layers with their centers of gravity distributed randomly in the plane of the layers and their axes parallel to the normal to the layers (called director) It is a sort of two-dimensional liquid in the plane of the layers and a solid in the direction of the director.

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