Columnar order

In the mesophase, the molecules exist in a discotic hexagonal columnar ordered stmcture, schematically shown in Figure 4. 

The columnar order in 52a,b was explained by molecular folding the molecules are assumed to be in their U- (or wedge-) shaped conformation and six molecules self-assemble to a supramolecular disc. These discs are stacked in columns and arranged within a columnar hexagonal lattice (Fig. 8). Folding of similar mesogens was also seen by Heiney [65]. 

Terminal crown ethers with taper-shaped substituents often possess columnar phases. Sometimes, the columnar order is only observed after the complexation of specific salts. The uptake of salts often results in the crown ethers assembling side by side forming supramolecular cylinders with the crown moieties on the inside and the alkyl chains on the outside leading to possible ion-conducting arrangements within an insulating jacket. Indeed, it was shown that matrix-fixed tubular arrangements are ion conductors. 

It has to be noted that only the (001) reflection accompanied by a wide-angle halo was observed which would also account for a smectic phase. Yet, the textures indicate a columnar order. 

If this is not possible, the columnar order gets lost (133) or smectic layers are favored (132). 

In a hard-rod system, at sufficiently high volume fraction a transition is usually expected from the nematic to the smectic A phase [37], a lamellar phase with layers perpendicular to the nematic director. However, as elegantly demonstrated by Livolant [29], in DNA the smectic phase is replaced by columnar ordering this behavior can easily be explained on the basis of strand flexibility [38] or length polydispersity [39], both favoring the COL phase over smectic. 

Guillon D (1999) Columnar Order in Thermotropic Mesophases. 95 41-82 Giitlich P (1981) Spin Crossover in Iron(II)-Complexes. 44 83-195 Gutmann V, see Mayer U (1972) 12 113-140... 

Frenkel D 1989 Columnar ordering as an excluded-volume effect Liq. Cryst. 5 929-40... 

Columnar Order Through Specific Intermolecular Interactions. 68... 

When the molecular volume cannot be measured (mainly because the quantity of the sample is too small), an alternative method using only the lateral packing parameter of the columnar order, can be applied to determine... 

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