Liquid crystalline textures

Fig. 8. Liquid-crystalline textures of didodecyl-PPE 12c. Bars represent 20 microns. These PPEs form homeotropic smectic phases the textures are typical for an edge-on view of lamellae that show apparent nematic ordering in this projection [46],...

Lyotropic liquid crystalline properties were observed for poly (arylamide) monodendrons derived from 1,3,5-substituted amino acid chloride hydrochlorides according to Kim [168]. These systems aggregate readily to form high molecular weight species in the absence of complexing ions. Amide solvents containing more than 40 wt.% of the dendrons exhibit nematic phase liquid crystalline texture under a polarizing microscope, whereas, 60 wt.% solutions produce a hard gel under static conditions. 

Two papers published in 1991 described the thermal properties of the diester ferrocene derivatives 8 [15] and 9 [16] (Fig. 9-4). Complexes 8 (n = 3, 4, 6, 8) were found to be non-mesomorphic and 8 (n = 10) seemed to give rise to a smectic phase (unidentified) between 85 °C and 88 °C during the second heating cycle. When 9 n = 1) was cooled from the isotropic melt at a rate of 2 °C/min, a liquid crystalline texture was observed (transition temperatures and liquid crystalline range not given) that, according to the authors, was indicative of a smectic phase. The latter was not identified. Derivative 9 n = 10) formed a nematic phase between 78 °C and 79 °C. This mesophase did not reform on cooling from the isotropic melt. 

Figure 4. Liquid crystalline texture of Ci diphosphate derivative.

Y. Kawanishi, T. Tamaki, T. Seki, M. Sakuragi, Y. Suzuki, and K. Ichimura, Multifarious liquid crystalline textures formed on a photochromic azobenzene polymer film, Langmuir 7,1314-1315 (1991). 

Guan L, Zhao Y. 2001. Self assembled gels of liquid crystals hydrogen bonded aggregates formed in various liquid crystalline textures. J Mater Chem 11 1339 1344. 

Liquid crystalline textures in polymeric systems can be obtained in two different ways. One way consists in inducing a specific texture in a liquid crystalline monomer phase. Often the forces acting on the sample will be sufficiently large to stabilize the texture during the polymerization. A texture may be obtained in this way even in polymers which do not display liquid crystalline phases. In the case of polymer 3 the polymerization in the nematic monomer phase under the influence of a magnetic field led to a polymer sample with high orientational order on a macroscopic scale. 

A second way to obtain liquid crystalline textures consists in heating up polymer samples, which display liquid crystalline phases, between glass slides or under the influence of external forces such as electric or magnetic fields. Textures will then form in a way similar to the case of low molecular weight liquid crystals. This was observed for the case of the polymers 1. On cooling down the textures can be frozen in since a glass transition occurs. Thus it becomes possible to keep a specific texture with interesting optical properties permanently. 

The heat of transitions, AHd h) in high melting peaks, is almost independent of tc- This implies that there is always a frozen liquid crystalline phase when quenching this polymer from 400°C to room temperature. In other words, the formation of liquid crystals from the isotropic phase can proceed very rapidly. Similar observations have been reported for a polyimide LCP quenched from 350°C in air and exhibiting a fine frozen liquid crystalline texture under polarized light microscopy [64,65],... 

Liquid crystalline textures were investigated by POM and thermal transitions in a glass-forming polydomain nematic network (liquid crystalline polyester, P5tB) showing an SME were determined [54], Two transitions, both nematic-isotropic could be detected from experiments with hot-stage POM. 

Figure 6. Optcal micrographs of liquid-crystalline texture in PBTA fibers, magnification, 400x, under polarized light.

For rod-like molecules theory predicts the formation of liquid-crystalline textures which have not been found so far. 

An Olympus polarized microscope-equipped camera was used to observe the liquid-crystalline textures between two glass plates. The textures at rest... 

Very clear evidence for smectic textures in dispersions of the bacterial viruses Pf 1 and fd was obtained by Booy and Fowlei by freeze-fracture electron microscopy. The liquid-crystalline textures revealed by this technique correlate well with polarizing microscopy of magnetically oriented specimens. 

Giambtaini M, Amendola E, Carfagna C (1997) Lightly crosslinked liquid crystalline epoxy resins the effect of rigid-rod length and applied stress on the state of order of the cured thermoset. Mataomol Chem Phys 198 3185—3196 Grebowicz JS (1996) On the formation of liquid crystalline texture in epoxy resins. Macromol... 

Polymers in which the mesogenic group is connected to the main chain via a flexible spacer display liquid crystalline textures characteristic... 

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