Focal textures

While such behavior can be seen in achiral LC phases, driven by surface constraints as illustrated in Figure 8.11, further characterization of the phase responsible for the minority domains in the B2 banana phases shows this to be the first unequivocal example of a bulk fluid conglomerate. It is worth noting here that the EO behavior of the majority domains is achiral Stripes parallel to the layers switch to a SmA-like focal conic texture, which is identical for both signs of the field, as can be seen in Figure 8.22. This EO behavior very clearly appears achiral when observing the switching in motion. 

Application of a field to the ShiCaPa phase causes switching by precession of the director around the tilt cone in alternate layers, to give a ferroelectric ShiCsPf state with uniform tilt. In this case, there can be no domains of opposite tilt since such domains would necessarily have their polarization opposing the applied field. This leads to a uniform SmC-like texture with a green birefringence color. The extinction brushes in the cylindrical focal conic rotate counterclockwise when the net tilt rotates clockwise, as indicated in Figure 8.25. As anticipated, the chiral rotation of the brushes is a direct manifestation of the chirality of the phase. Elsewhere in the sample there must be ShiCaPa domains of opposite handedness, which would possess the opposite sense of tilt for the same sign of the applied field. 

Figure 8.34 Left Gold focal conics of MHOBOW coexisting with accordion domains in 4-p.m SSFLC cell. Cell has not seen electric field. Right Same area after brief application of field above threshold for causing textural change of focal conics from gold SmA-like to bistable blue SmC -like. Transition from gold to bistable blue is still incomplete in this photomicrograph clear domain walls between two textures are easily seen.

Texture composed of focal-conic domains of the ellipse-hyperbola type with visible ellipses, or parts of ellipses, located at the boundary surfaces. 

Texture formed partly by focal-conic domains with their hyperbolae lying in the plane of observation. 

Fig. 25. Arrangement of a smectic A polygonal texture (a) general view of the focal-conic domains filling space efficiently (b) cross-section of the domains showing arrangement of...

Lamellar focal conics show a fascinating highly-ordered structure when observed under the polarization microscope. This texture consists of surfactant bilayers that are shaped like ice cream cones and stuck inside of one another. These stacks of cones are quite densely packed in the solution and, under the polarization microscope, create extended regions of amazing regularity. Figure 3 shows a photograph of such a system, taken with a polarization microscope with a A mask to achieve color contrast. 

Recently, Sato and Hatano 67 69) found a new type of chiral lyotropic mesophase composed of Tween 80, sorbitan mono-9-octadecenoate poly(oxy-l,2-ethanediyl), and water, and discussed the ICD of achiral solute molecules intercalated into the lyotropic mesophase. As the concentration of Tween 80 is increased, three distinct phases are obtained micelle, neat phase, and reversed micelle, in that order. In the region of the volume ratio of Tween 80/(Tween 80 + water) of 0.40 to 0.63 under crossed Nicol-prisms, a focal conic texture was observed. This result indicates that the... 

Fig. 9 Textures of the columnar phases of compound 34b. Pseudo-focal conic texture at 92 °C of the Colhd phase (bottom) and at 74 °C in the body-centred orthorhombic columnar phase (top). In order to increase the dynamic range of the photographs various photos with different exposure times have been superimposed. The black Maltese cross is perfectly dark in the centre for the Colhd- In the low temperature phase undulation of the columns produces birefringence in the dark branches...

F. Andermann, and D.L. Arnold. 2001. Texture analysis and morphological processing of magnetic resonance imaging assist detection of focal cortical dysplasia in extra-temporal partial epilepsy. Ann. Neurol. 49 770-775. 

Fig. 9-11. Representative thermal polarized optical micrograph of the focal-conic texture displayed by 14 (n = 12) in the smectic A phase on cooling from the isotropic liquid to 164 °C.

Ferrocene derivatives 15 exhibited remarkable liquid crystal properties (Fig. 9-13). Indeed, they all gave rise to enantiotropic mesophases. Structures with n = 1 to 11 showed nematic phases. From n = 12 a smectic C phase formed. The latter was monotropic only for 15 (n = 12). The smectic C domain increased from n = 13 to n = 16, and, inversely, the nematic range narrowed. The last member of this series (n = 18) presented one smectic C phase between 159 °C and 179 °C. A nematic to smectic C transition and a focal-conic texture of a smectic C phase are presented in Figs. 9-14 and 9-15, respectively. 

By polarizing light microscopy we saw the typical focal conic smectic texture of the BDVHD hcmopolyester mesophase but observed no distinctive smectic or nematic structure of the BDA/50 EG/50 HD copolyester cooled from the isotropic melt and held in the mesophase many hours. Also on an x-ray diffractometer trace of the copolyester we did not see the characteristic peak due to the spacing between the layers of the smectic mesophase but did see... 

In the THF insoluble fraction (BP6Li), the observation of a focal conic texture as well as the presence of batonnets prior to clearing leads... 

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