Columnar liquid crystal

In addition to the nematic phase (termed Nq), disc or bowl-shaped molecules may stack in layers (discotic smectic), or much more often, to columns forming so-called columnar (Col) discotic or columnar pyramidic 

Nematic (N ) Smectic (Sm J Columnar (CoL ) PACKING WITHIN COLUMNS 

Schematic illustration, classification and nomenclature of discotic liquid crystal phases. For the columnar phases, the subscripts are usually used in combination with each other. For example, Col, denotes a rectangular lattice of columns in which the molecules are stacked in 

Discotic and bowl-shaped molecules that form columnar phases, (a) Hexa-alkanoate [R=CH3-(CH2) -2C00-] of triphenylene (b) hexa-noyloxy-tribenzocyclononene, which forms a polar pyramidlc phase (c) l,2,5,6,8,9,12,13-octakis-((S)-2-heptyloxy) dlbenzo[e,l]pyrene, which has chiral therminal chains and forms tilted ferroelectric columnar liquid crystal.  

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McMillan s model [71] for transitions to and from tlie SmA phase (section C2.2.3.2) has been extended to columnar liquid crystal phases fonned by discotic molecules [36, 103]. An order parameter tliat couples translational order to orientational order is again added into a modified Maier-Saupe tlieory, tliat provides tlie orientational order parameter. The coupling order parameter allows for tlie two-dimensional symmetry of tlie columnar phase. This tlieory is able to account for stable isotropic, discotic nematic and hexagonal columnar phases. 

Serrette, A.G. and Swager, TM. (1994) Polar Superstructures Stabilized by Polymeric Oxometal Units Columnar Liquid Crystals Based on Tapered Dioxomolybdenum Complexes. Angewandte Chemie (International Edition in English), 33, 2342-2345. 

Knight, D., and Vollrath, F. (1999a). Hexagonal columnar liquid crystal in the cells secreting spider silk. Tissue Cell 31, 617-620. 

Discotic liquid crystals arise from disk-shaped molecules as nematic or cholesteric mesophases. Their structural characteristics are similar to the respective ealamitie mesophases, that is, the normals of the disks are oriented parallel. Instead of the smectic mesophases, diseotie columnar liquid crystals arise from eonnecting the disks to each other. The columns of the discotic columnar mesophase form a two-dimensional lattice whieh is in a hexagonal or rectangular modification. In addition, the columns may be tilted (Fig. 2f,g). 

Oswald P, Pieranski P (2006) Smectic and columnar liquid crystals. Taylor Francis, Boca Raton... 

Columnar liquid crystals consist of flat, disc-shaped molecules aligned in columns. These columns may be arranged in a hexagonal pattern as illustrated in Figure 16.4. 

In columnar liquid crystals flat molecules are aligned in columns. 

Organic Light-Emitting Diodes Using Low-Molar-Mass Materials (LMMMs) 161 Table 5.5 Transition temperatures CC) for the columnar liquid crystals (17-21)... 

A further potential problem associated with the practical fabrication of multilayer OLEDs with low-molar-mass calamitic and columnar liquid crystals with a charge-transport layer, especially as the HTL, is the fluid nature of the liquid crystalline state. This could permit contamination of the columnar liquid crystal during the deposition of subsequent layers by the process of vapour deposition or spin-coating. The columnar materials could well be soluble in the solvent used to deposit the next layer. This would lead to chemical contamination of the individual layers due to mixing of one component into another, the... 

Axial motion of discs in columnar liquid crystals... 

Kato and coworkers reported the preparation of one-dimensional conductive films containing ion channels formed by self-organization of polymerizable columnar liquid crystals [93]. Such films were obtained by photopolymerization of aligned columnar liquid crystals of a fan-shaped imidazolium tetrafluoroborate salt, having acrylate groups at the periphery, as in 39 and 40. 

Yoshio M, Kagata T, Hoshino K et al (2006) One-dimensiontil ion-conductive polymer films alignment and fixation of ionic channels formed by self-organization of polymerizable columnar liquid crystals. J Am Chem Soc 128 5570-5577... 

Fig. 2 Molecular structure of a columnar liquid crystal having a crown ether moiety...

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