Amphiphilic Liquid-Crystals

J. M. Garcia Fernandez, A. Gadelle, and J. Defaye, Difructose dianhydrides from sucrose and fructooligosaccharides and their use as building blocks for the preparation of amphiphiles, liquid crystals and polymers, Carbohydr. Res., 265 (1994) 249-269. 

Figure 1.14. The amphiphilic liquid crystals. (From Codings, 1990.)...

The special restriction caused by tying low molecular mass liquid crystalline substances to a polymer chain was also illustrated with amphiphilic liquid crystals. A hexagonally close-packed structure of rod-like micelle cylinders of sodium 10-undecenoate with about 50% water lost during polyma-ization at 60 °C its structure and became isotropic. On cooling, a lamellar liquid crystalline structure, more suitable to accommodate the macromolecular backbone was found. Bas l on the discussions of Sect. 5.3.4 it is likely that with longer side-chain amphiphiles condis crystals could be grown in analogy to the soaps described in Sect. 5.2.3... 

Cubic phases have long been known in the field of amphiphilic liquid crystals (surfactants [97] and lipids [98, 99], and have been studied extensively. For example, it has recently been proved that lyotropic, cubic phases play an important role in the control of biological processes such as membrane fusion, fat digestion and the ultra-structural organisation of cells [100]. They have also... 

The columnar phase of amphiphilic liquid crystals is most often of a hexagonal disordered type. Only a very few examples are known for rectangular [173-175] or monoclinic [173] columnar phases or for ribbon phases [176]. 

The last volume is devoted to polymeric liquid crystals (with chapters about main-chain and side-group thermotropic liquid crystal polymers), amphiphilic liquid crystals, and natural polymers with liquid-crystalline properties. 

Typical phase morphologies of block copolymers are illustrated in Figs. 5.38 0 and 5.79. In the classification of phases, the phase-separated block copolymers are considered to be amphiphilic liquid crystals despite the fact that inside the phase areas the typical liquid-crystalline order is missing (see Sect. 5.5). In this section the question will be addressed what happens when the usually micro- or nano-phase separated block copolymers show solubility, i.e., when the amphiphilic liquid crystal becomes thermotropic, i.e., dissolve at a given temperature. 

Table 7.1. Quadrupole Splittings of Halide Ions in Amphiphilic Liquid Crystals at...

Acid anhydrides, 391 Amino hydrochloride water solutions, lyotropic phases, 306-308,310/ Amorphous polyimide-liquid-crystalline polyamide composites. See Liquid-crystalline polyamide-amorphous polyimide composites Amphiphilic liquid crystal(s), establishment, 235,236/... 

Sugars are a commonly used source for amphiphilic liquid crystals [10]. These materials show lamellar, columnar, and cubic phases, but chiral phases are very rarely observed. Thermotropic cholesteric phases are never observed and lyotropic cholesteric phases based on asymmetric micelles only in a few cases [11]. The bicontinuous cubic phase of these glycolipids may have macroscopic chiral ordering, but this has not been resolved hitherto [12], [13]. Thus, alkylated sugars are chiral compounds, but not effective... 

Liquid crystalline amphiphilic diblock copolymers poly(ethylene oxide)-h/oc -ll-[4-(4-butylphenyl-azo)phenoxy]-undecyl methacrylate, PEOn,-h-PMA(Az) , as shown in Fig. 16, prepared by atom transfer radical polymerization [61], were composed of hydrophilic PEOn, sequences and hydrophobic PMA(Az) , with azobenzene moieties such as mesogen connected by a flexible spacer. The synthesis of such amphiphilic liquid crystal block copolymers has been recently reported [62]. In diblock copolymers PEO ,-h-PMA(Az)n, m and n indicate the degree of polymerization of PEO and PMA(Az) components, respectively. Differential scanning calorimetry (DSC) of PEO ,-f>-PMA(Az)n gives a clear picture of the thermal properties of these liquid crystaUine polymers, as shown in Fig. 17, for PEOn4-h-PMA(Az)2o [58, 61]. 

Mesophase origin Amphiphilic liquid crystals Monophilic liquid crystals... 

Liquid crystalline diols may be considered as having a structure intermediate between that of non-amphiphilic and amphiphilic liquid crystals, i.e. like soaps, ten-sides, phospholipids and sugars. Compound 26 [255] exhibits phases that are similar in... 

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