Mesophase optical micrograph

Figure 7. Optical micrograph of VII showing texture of the mesophase at 182 °C. Magnification 320 X.

The mesophases of LC diols la-lg were also observed directly in polarized optical micrographs taken immediately after melting the sample. Textures were identified only by comparison with published micrographs (2 ), and are therefore tentative. A nematic texture is observed for If (Fig. 2), while more highly ordered smectic textures are observed for Ib-le and Ig (Fig. 3). 

Figure 9. Optical micrographs of recrystallized THFI-PS fractions from a) A240- and b) CTP-derived mesophase pitches.

Striking evidence for chiral liquid crystallisation in vivo has been collected by Bouligand and co-workers. Optical micrographs of stained sections of crab (Carcinus maenas) and insect (Locusta migratoria) cuticle for example, reveal the single twist characteristic of the cholesteric mesophase (Figure 6). 

Typical polarized optical micrographs of the molten samples were shown in Figure 1. Microscopic analyses were earned out at temperatures in the range 25 - 390 C, and threaded textures, a characteristic optical texture of nematic mesophase, were observed above LCITs over the investigated composition range. The nematic to isotropic transitions were not observed up to 390 C. 

Fig. 4.7 Optical micrograph of 23 (n = 5, R = qH,) in the columnar mesophase at 78°C (Reproduced from Ref [50] with kind permission of Elsevier)...

Figure 2.3S, Figure 2.36. Optical micrograph of spheres of mesophase as developed during the carbonization of anthracene (left). Drawing of stacking arrangements of mesogens parallel to an equator of the sphere (right) (Marsh, unpublished results).

Fig. 1. Optical micrographs of the nematic mesophase of (a) 40/60 (PET/PHBA) and (b) 20/80 (PET/PHBA) composition...

Fig. 3. Optical micrograph ofordered nematic mesophase of40/60 (PET/PHBA) obtained by shearing at 290 °C and cooling to ambient temperature.

Figure 8). The enthalpy and entropy changes associated with these transitions are summarized in Table 4. Presently we do not know the degree of crystallinity of these polyethers. However, the fact that the enthalpy and entropy changes of all transitions are larger than those of melting seems to indicate that the polyethers exhibit multiple smectic mesophases. Additional support for smectic type mesophases are provided by their high viscosity and by the optical polarizing micrographs which exhibit mosaic textures, typical of higher ordered smectic phases, or batonnets textures,...

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