Rectangular columnar phase

Discotic LC are formed by disk-like molecules with aromatic cores and side chains that are either hydrophobic (i.e., thermotropic) or hydrophilic (i.e., lyotropic). The discotic nematic (No) phase behaves like a normal nematic phase formed by rod-like molecules, and the disk-like molecules are oriented with their short molecular axes parallel to the director but show no positional order. More ordered columnar phases are commonly formed by thermotropic discotics. The two-dimensional structure can pack the columns into a hexagonal or rectangular columnar phase, while within the columns, disks can be... 

Acyclic carbohydrates with two alkyl chains have been studied in detail in the case of dialkyldithioacetals 9. It is one of the more complete series whose results have been cross-checked and compiled [43]. Their liquid crystalline properties were compared with those of dodecyl a- and -D-glucofuranosides [50] depending on their structures, they form either hexagonal disordered columnar phases or a new rectangular columnar phase [77]. 

Compounds 1-3 exhibit mechano- and/or thermochromic photoluminescent properties accompanied by cubic-columnar LC phase transitions. Table 1 shows the LC properties of compounds 1-3. Compounds 1 and 3 show cubic phases and columnar phases on rapid cooling and slow cooling, respectively. A columnar phase is not observed for compound 2 on cooling. The differential scanning calorimetry (DSC) measurements of compounds 1-3 show that the cubic phases of compounds 1-3 are metastable phases, while the columnar phases are stable. The X-ray diffraction patterns indicate that compounds 2 and 3 form Pmhn cubic phases and PH a rectangular columnar phases. 

Atzner, F., Zantl, R., Rapp, G. and Radler, J.O. (1998) Observation of a rectangular columnar phase in condensed lamellar cationic lipid-DNA complexes. Phys. Rev. Lett., 81, 5015-5018. 

Figure 13.20 Orientated monodomain X-ray diffraction images from the dodecyloxy analogue of the compound shown in Figure 13.19 at (a) 104 °C and (b) 82 °C corresponding to hexagonal and rectangular columnar phases respectively (reprinted with permission from [11] 2004 American Chemical Society).

Coir rectangular columnar phase p2gg or c2mm symmetry)... 

Fig. 38 Schematic representation of the molecular model for codendrimers with one- and two-terminal-chain mesogenic imits (SmC and rectangular columnar phases)...

Serrano has also reported related mesomorphic rhodium(Il) alkanoate complexes, where the 4-alkoxybenzoato complexes display a rectangular columnar phase and a... 

Spontaneous polarisation can also be observed for chiral discotic metallomesogens forming columnar mesophases, when the chiral molecules are tilted with respect to the column axis. The tilt induces a dipole moment within the plane of the molecule. A net macroscopic polarisation can be obtained for rectangular columnar phases with Cz or P2i symmetry. Serrano and Sierra reported on ferroelectric switching in the columnar mesophase for chiral /3-diketonate complexes (Figure 2.52). ... 

Figure 12 Representations of the lattices of the (a) hexagonal, (b) oblique, and (c) and (d) rectangular columnar phases.

Fig. 11. Model proposed for the rectangular columnar phase of bis-swallow-tailed molecules...

Although all of the compounds studied form columnar phases, differences between them become apparent according to the metal involved in the complex. Thus, the fluxional complexes (Fe(III)-(6.36) and Mn(III)-(6.36)) exhibit a hexagonal columnar phase (Colli) at low temperatures, whereas the nonfluxional complexes show a rectangular columnar phase (Coif). In the case of the Colh phase, microdomains composed of (A) or (A) configuration are present. This arises due to the possible... 

Fig. 5.25 Dependence on length of the lat xil chain and rigid core, mesophases sequence formed by T-shaped bolapolyphiles with nonpolar (alkyl or semiperfluoroalkyl) lateral chains [9, 137, 138], Abbreviations SmA smectic A phase Col rectangular columnar phase Col g square columnar phase Col/ hexagonal columnar phase Lcarti, Lanifi, Lamg laminated phases with different ordta of the rodlike units Cub bicontinuous cubic phase, branched axial rod-bundles Col/ f hexagonal columnar phase formed by non-branched axial rod-boundles...

FIGURE 46 6,6 -Substituted 2,6-/ /5 (l-ethyl-benzimidazol-2-yl)pyridmes and their transition temperatures (in °C). Abbreviations Cr — crystalline phase, Coir — rectangular columnar phase, / = isotropic liquid. 

Cr, crystalline phase Coir,. rectangular columnar phase 1, isotropic liquid. ... 

Figure 4.3 shows the molecular arrangement of the rectangular columnar phase (D, ... 

A conqtlication is that rectangular columnar phases have been found with three different two-dimensional lattices, having the space group notations P2 /a, T 2/a ... 

Figure 11-4. Molecular positions within the hexagonal columnar phase (left) and rectangular columnar phase (right)...

Even though no tabular data are available for truxene derivatives, inclusion in this Datareview is important because these materials exhibit discotic nematic phases. The truxene phase data presented by Busine and co-workers [11] are for the transition of the discotic nematic phase to the disordered rectangular columnar phase (TABLE 18). Over the phase range studied which was up to 900 bar, the relationship between T and p is most conveniently represented as linear. Once again the magnitudes... 

Figure 11.3 Postulated supramolecular organization of 15 and 16 within the rectangular columnar phase.

Figure 11.7 Postulated supramolecular organization of 20 within the rectangular columnar phase of c2mm symmetry. Compounds 21 (Col,.p2gg) and 22 (Col,. 2 ) gave a similar organization.

Fig. 1.15 The structure of the tilted hexagonal columnar CoLd (C2/m) phase. The letter r indicates that the columns lie on a two-dimensional rectangular lattice and the letter d indicates that the stacking within the columns is disordered. The additional details given in brackets are the three-dimensional space group designation. It is necessary to add this, if one wishes to distinguish between this structure and that of other tilted rectangular columnar phases as shown in Fig. 1.14...

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