Hexagonal mesophase

Figure C2.3.13. Nonnal (H, left) and inverse (H, right) hexagonal mesophases composed of rodlike micelles.

Table 1 Thermal and geometrical data of selected semiflexible polymers giving rise to thermotropic hexagonal mesophases or main-chain disordered crystalline phases (adapted from [11])... 

We examine briefly some specific instances starting with syndiotactic polypropylene (sPP). Aside from the already discussed hexagonal mesophase which can be obtained both drawing fibers and under quiescent conditions, this polymer presents four crystalline forms phases I [73] and II [74-76] where chains adopt the (T2G2)n helical conformation, forms III [30] and... 

In addition to the cubic and/or inverse cubic forms described above, further transitional forms exist between the lamellar phase and the hexagonal mesophase (cubic, type II) or inverse hexagonal mesophase (cubic, type III) [6]. In contrast to the discontinuous phases of types I and IV, cubic mesophases of type II and III belong to the bieontinuous phases (Fig. 4f). A range of lyotropic mesophases are possible, depending on the mesogen concentration, the lipophilic or hydrophilic characteristics of the solvent, and the molecule itself [6]. 

Hexagonal mesophases can be recognized by their typical fan-shape texture (Fig. 7a). Lamellar mesophases typically show oily streaks with inserted maltese crosses (Fig. 7b). The latter are due to defects, called confocal domains, that arise from a concentric rearrangement of plane layers. In some lamellar mesophases these defects prevail. Hence no oily streaks occur but maltese crosses are the dominant texture (Fig. 7c). 

Figures 9a-c represent transmission electron micrographs of different lyotropic liquid crystals after freeze fracture without etching. The layer structure of the lamellar mesophase including confocal domains, hexagonal arrangement of rodlike micelles within the hexagonal mesophase, as well as close-packed spherical micelles within the cubic liquid crystal can be clearly seen.

Advances in the chemistry of [M(CN)5L]" complexes, for M = Fe, Ru, and Os, have been reviewed.There has been rather little activity in the preparation of novel complexes, but considerable activity in studying the properties, especially solvatochromism and various aspects of kinetics of substitution, of known complexes. However there has been an attempted preparation of [Fe(CN)5(Ci2H25NH2)], in the hope of generating micelles or lyotropic liquid crystals. This preparation appeared to yield [Fe(CN)4(H20)(Ci2H25NH2)], whose alkali metal salts gave a hexagonal mesophase in water, but were also readily hydrolyzed to [Fe(CN)4(H20)2] . Heterobinuclear complexes of the form [(NC)5FeL ML 5] " " have been much studied, especially in relation to intramolecular electron transfer (see Section 5.4.2.2.5). 

Fig. 14. Illustrating the molecular organization of a columnar hexagonal mesophase.

Note 4 The lyotropic equivalent of a columnar hexagonal mesophase is known as a hexagonal mesophase in it, columns of amphiphilic molecules are surrounded by the solvent, normally water, or an oil in an inverse hexagonal mesophase. 

When the PTES/TEOS ratio exceeds 1 4, a hexagonal mesophase is again formed. SEM observation of the 1 1 powder shows two types of grain morphology aggregates of facetted... 

The characterisation of the hexagonal mesophase (i.e. of the samples with low amounts of the other phase) reveals a number of significant properties (i) The [Pg.561]

In this section, crown ethers will be discussed which are equipped with one taper-shaped substituent (Fig. 10). Columnar hexagonal mesophases are the most commonly observed phases in this kind of molecule. 

Upon addition of NaOTf, columnar hexagonal mesophases could be induced. For 68, 0.4 equiv. of salt were needed while for 67, only 0.2 equiv. of NaOTf were needed for mesophase induction. Upon complexation, the complexed crown ether moieties and the anions self-assemble within a supramolecular tube and the taper-shaped side groups stack over each other in the periphery. X-Ray scattering... 

He and Cammidge prepared liquid crystal 113 (Scheme 59) with a central [27] crown-9 moiety, three attached triphenylene units carrying a total of 12 hexyloxy chains and exhibiting a columnar hexagonal mesophase [122]. 

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