Wedge columnar phases

Fig. 6.4.4. Disclinations in the columnar phase (a) and (b) —n/i and ff/3 longitudinal wedge disclinations about the sixfold axis L (c) and (d) n transverse wedge disclinations about the binary axes and 0 respectively (e) -n transverse wedge disclination leading to the formation of walls (/) two n disclinations at right angles to each other, one about 7 and the other about 0. (Bouligand. ")...

The symmetry of the columnar phase also permits the occurrence of twist disclinations in the hexagonal lattice and of hybrids consisting of a twist disclination in the hexagonal lattice and a wedge disclination in the director field. According to Bouligand these defects are not likely to exist. 

Fig. 15 The molecules with wedge-like structures (a) can stack to form columns where for the columnar phase the molecules are disordered relative to the column axis, with the columns organised into rectangular or hexagonal arrays (b).

Some salt-like compounds with wedge-shaped molecules (e.g. 34 [309] and 35 [310]) show columnar phases over wide temperature ranges. 

Both the twin-wedge complex and the unpolymerized analog exhibited enantio-tropic hexagonal columnar LC phases, based on a repeating four-cylinder bundle pattern, as confirmed by X-ray diffraction (Fig. 7.8). 

Wedge-shaped dendrons such as those described above form mainly columnar and cubic phases. However, a liquid-crystalline phase with a tetragonal three-dimensional unit cell (Tet phase) containing 30 globular supramolecular dendrimers has been reported recently. Each of these supramolecular dendrimers is the result of the self-assembly of 12 dendrons, as is shown in Fig. 8 [120,121]. Interestingly, the complex tetragonal phase of symme-... 

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