In liquid crystals, texture is the polarization microscopic appearance of their mesophases . Such textures are specific to the different mesophases (nematic, smectic, columnar etc.) within certain limits and are used for their preliminary determination.
The nematic droplet texture appears at the transition from the isotropic phase to the nematic mesophase in the form of birefringent droplets of the nematic mesophase. These droplets have a characteristic appearance due to defects ( bipolar or radial droplets).
Droplet texture (bottom left) of a nematic phase.
The streak texture is characterized by the appearance of a dense network of black bands ("streaks"), which connect the cores of point and line defects .
Schlieren texture of a nematic phase.
Smectic textures
During the transition from the isotropic liquid phase or a nematic phase to the smectic A or C phase, the latter often appear as so-called Bâtonnets , which steadily displace the old phase.
Bâtonnets of a smectic C phase grow into the streak texture of a nematic phase.
The focal-conical fan texture is a very common texture found in smectic A and C phases.
Fan texture of a smectic C phase.
Polygon texture
Polygon texture of a smectic A phase.
More textures
So-called mosaic textures are characteristic of z. B. smectic B and columnar phases.
Mosaic texture of a right-angled columnar mesophase.
Spherulitic textures are regularly found for columnar phases. Spherulites are also called circular domains and are based on a specific arrangement of the molecules in these domains.
Spherulitic texture of a right-angled columnar mesophase
Both textures, mosaic texture and spherulite, can also appear together.
Mosaic texture with embedded spherulite, right-angled columnar mesophase.
The most varied and most impressive textures are probably shown by the phase, an exotic mesophase type of so-called "banana-shaped" ( bent-core ) mesogens.
Texture of the B7 phase of a "banana-shaped" liquid crystal.
Texture of the B7 phase of a "banana-shaped" liquid crystal.
Günter Jakob Lauth, Jürgen Kowalczyk: Introduction to the physics and chemistry of interfaces and colloids . Springer, Berlin, Heidelberg 2016, ISBN 978-3-662-47017-6 , Chapter 13: Liquid Crystals , doi : 10.1007 / 978-3-662-47018-3_13 .
