Conoscopic figure

Fig. 6.6.2. Conoscopic figure demonstrating the biaxiality of the nematic phase of...

Figure 9.19. Typical conoscopic figures, indices of ellipsoid, and molecular arrangements in the SmC, SmCy, and SmC phases under appropriate electric fields.

Figures. Conoscopic figures (a) biaxial nematic phase of pure complex 2 at =1.5 °C (b) uni-...

Figure 7. Conoscopic figures of an aligned sample of 2,3.4-trihexyloxycinnamic acid dimer (compound 3, R = n-C6H 3) in its nematic phase on the left rotated 0° on the right 90° (from [23]).

Figure 25.9 Polarizing optical micrographs of the equimolar mixture of 14 and 16 in the smectic A liquid crystalline state (a) homeotropically aligned monodomain is formed on a glass substrate when the sample is cooled slowly from the isotropic state at the rate of 3° C min Inset is a conoscopic image (b) unaligned polydomains are formed on a glass substrate when the sample is cooled from the isotropic state at the rate of 20°C min ...

Figure 11.18 Predictions of the tumbling parameter A as a function of reduced concentration C/C2 from the Smoluchowski equation for hard rods with the Onsager potential. The exact result from the spherical-harmonic expansion is shown, compared to approximate results from an analytic formula and from the perturbation expansion of Kuzuu and Doi. The open circles (O) are estimates from the periods of shear stress oscillations in transient shearing flows for PEG solutions (see Walker et al. 1995), and the closed circle ( ) is from a direct conoscopic measurement of Muller et al. (1994).

In studies of the optical properties of the liquid crystal phase the microscope may be arranged for orthoscopic observations between crossed polars, or it may be arranged for conoscopic observations. These two arrangements are shown in Figure 4.4. 

Figure 4.4. Polarizing microscope for orthoscopic (a) and conoscopic (b) observations.

Figure 4.11. Determination of optical sign by conoscopic examination with insertion of a compensator.

Figure 25. Eliipsoidofindicesforapositive(nj>/io) uniaxial LC. The typical conoscopic images with average beam direction perpendicular to the plates are shown for (a) homeotropic, (b) planar and (c) oblique orientation (31].

Interference figure n. The conoscopic pattern of extinction positions of a crystal superimposed on the pattern of interference colors corresponding to the full cone of directions by which the crystal is illuminated, each direction showing its own interference color. 

Figure 10. Conoscopic observation of induced alignment change of PMeOAzO/DON103/ODS cell by slantwise exposure to UV (a) and visible (b) lights. Exposure was made from the left of the microscope. Pictures were taken every 2s for (a) and 0.5s for (b) as the order shown above the pictures.

Since conoscopic experiments require macroscopic uniformly oriented samples, mixtures of the polymer with 30%, 40% and 50 % of a cyanophenylester, a low molar mass liquid crystal, were investigated. The addition of a low molar mass liquid crystal serves to lower the glass transition temperature and consequently the rotational viscosity. These mixtures could therefore be oriented using a procedure that is depicted in Figure 5-7. 

Samulski and co-workers [32] investigated two different bent-core mesogens, where the core consisted of an oxadiazole and the aliphatic chain R in the structure shown in Figure 5-19 was either an OC12- or a C7-unit. Figure 5-20 shows polarization microscopy pictures as well as conoscopic results for the OC12 sample. 

All PCH and BPpolymers with liquid crystalline groups in the side chain exhibited fanshaped textures and uniaxial conoscopic patterns in a polarizing optical microscope that are characteristic of the smectic A phase. Typical fan-shaped textures of the polymers prepared with Fe-based and Mo based catalysts are shown in Figure 9-3. 

Figure 3 Conoscopic pattern taken with crossed polars. The sample is a uniaxial crystal with its optic axis parallel to the axis of the microscope. The dark cross shows the polarization directions for the polarizer and the analyzer. The rings are at retardations of 1,2, and 3 wavelengths.

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