Cubic mesomorphic phases

Balmbra R R, Clunie J S and Godman J F 1969 Cubic mesomorphic phases Nature 222 1159-60... 

Balmbra, R. and Clunie, J. (1969) Cubic mesomorphic phases. Nature (London), 222, 1159. 

Only a limited number of studies of cationic surfactant-water systems have been reported. Fig. 2.6 shows the phase behaviour for the binary system dodecyltrimethylammonium chloride-water [23]. The interesting feature of this binary System is the appearance of two distinct cubic mesomorphic phases. An extensive range of techniques including optical microscopy, differential thermal analysis, proton magnetic resonance and low-angle X-ray diffraction were used to... 

V. Homogeneous viscous isotropic mesomorphous phase displaying cubic structure. 

V. Homogeneous viscous isotropic mesomorphous phase displaying cubic structure. From Ekwall et al. [27] with permission. 

Having found that gold triflates were mesomorphic, we returned to silver and decided to look at other anions. In so doing, we made complexes of silver trifiate and nitrate, each of which exhibited similar patterns of liquid-crystal behavior namely, the formation of Sc and Sa phases at rather elevated temperatures (the phase diagram for the nitrates is reproduced in Fig. 40) (54). While neither of these systems showed a cubic phase, we did find a nematic phase in the triflates. 

Amphiphilic lipopeptides with a hydrophobic paraffinic chain containing from 12 to 18 carbon atoms and a hydrophilic peptidic chain exhibit lyotropic meso-phases and good emulsifying properties. The X-ray diffraction study of the mesophases and of dry lipopeptides showed the existence of three types of mesomorphic structures lamellar, cylindrical hexagonal and body-centred cubic. Two types of polymorphism were also identified one as a function of the length of the peptidic chain and the other as a function of the water content of the mesophases. The emulsifying properties of the lipopeptides in numerous pairs of immiscible liquids such as water/ hydrocarbons and water/base products of the cosmetic industry showed that small amounts of lipopeptides easily give three types of emulsions simple emulsions, miniemulsions and microemulsions. 

We later investigated a series (Figure 107A) of surfactant /ris(bipyridyl)ruthen-ium(II) complexes first reported by Seddon [194], which we have shown to be mesomorphic in water [195]. Thus, consistent with the packing constraint ideas of Israelachvili developed above, single-chained derivatives (m=l, n= 12-31) showed Ii cubic mesophases, while double-chained derivatives ( =12, m=l2, 19) showed Hi hexagonal phases. For the mono-chained material with m — l and... 

The acetylide complexes 90 were synthesized on Pt rather than on Pd, due to the lability of the latter metal that precluded isolation of such species other than Pt. These species were accessed as neutral analogs of related Ag(l) complexes in order to try to delineate the effect on the mesomorphism of the charge on the silver complexes and how this might relate to the stability of the cubic phase seen extensively in the silver complexes.The Pt-acetylide complexes turned out to be predominantly nematic in their phase behavior and the consequences in relation to cubic phase behavior were discussed. Curiously, however, the complexes did, in addition, show a SmC phase. It is almost universally true that liquid crystals bearing lateral chains show only nematic phases,and so this aspect of the behavior of Pt complexes still requires explanation. 

Studies of the mesomorphic properties of 4-alkoxyphenyl-]3-D-glucopyranosides [102 b] reveal that these amphiphiles form a SmA phase on heating. Lyotropically, the usual phase sequence for single tailed carbohydrates (isotropic, columnar hexagonal, cubic, and lamellar with decreasing water... 

It is now certain that metal carboxylates were the first metal-containing liquid crystals, reported in 1855 with Heinz s work on magnesium tetradecanoate. Then, many other mesomorphic mono-, di-, and tri-valent carboxylate complexes, with the general formula [M(02CC H2 +i)J (x=l, 2, 3) or [M2(02CC H2 +i)4] were prepared. Some of them were described in 1910 by Vorlander." These materials may show thermotropic nematic, smectic, cubic, and columnar mesophases, but also, when dissolved in water or alkanes, lyotropic mesophases. While not all of the compounds described in this section show columnar phases, it was decided to keep these materials together. 

The absence of mesomorphism in these compounds was explained on the basis of space-filling requirements. Thus, the intercalation of pyrazine between the binuclear units creates free volume which needs to be filled to obtain a stable, condensed phase when the carboxylates bear only one chain, the interdimeric space is likely filled by the aliphatic chains belonging to a different polymeric chain, giving rise to a crossed structure which prevents the formation of a columnar mesophase. However, as will be seen later, liquid-crystalline behavior was induced in the case of mixed-valence diruthenium(II,III) carboxylate complexes with bulky equatorial Kgands bearing two and three aliphatic chains as with such ligands, it was possible to fill the interdimeric space and thus to induce a thermotropic columnar mesophase. Very recently, the synthesis, characterization, and mesomorphic properties of pyrazine-polymerized divalent rhodium benzoates have also been reported (99). " Most of these compounds exhibit columnar (Colh, Coir, CoIn) and cubic mesophases with melting transition temperatures close to, or even below, room temperature. 

The related trialkoxybenzoate copper complexes ((98) M = Cu) was also mesomorphic, between 75 and 85 °C and 110 and 130 °C, but the most intriguing feature was the change of the Colh phase (n= 10, 12, 14) into a Cub phase (n= 16, 18) with increasing chain length. The cubic phase was found to exist in the space Im3m group, but whether the phase is bicontinuous or micellar has yet to be established. 

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