Lyotropic liquids, layered assembly

These structures are extensively described in the current literature (Fanum, 2008 Friberg, 1976 Birdi, 2002 Holmberg, 2004 Somasundaran, 2006). Even within the same phases, their self-assembled structures are tunable by the concentration for example, in lamellar phases, the layer distances increase with the solvent volume. Lamellar structures are found in systems such as the common hand soap, which consists of ca. 0% soap + 20% water. The layers of soap molecules are separated by a region of water (including, salts etc.) as a kind of sandwich. The x-ray diffraction analysis shows this structure very clearly. Since lyotropic liquid crystals rely on a subtle balance of intermolecular interactions, it is more difficult to analyze their structures and properties than those of thermotropic liquid crystals. Similar phases and characteristics can be observed in immiscible diblock copolymers. 

The formation of layered assemblies can be induced by the addition of a small amount of water to isotropic ionic liquid l(10/Br ) [52, 53], A lyotropic liquid crystalline gel consisting of l(10/Br ) and water of 16wt% has been prepared. Addition of water to l(10/Br ) induces the formation of a lamellar structure with... 

It stabilizes the lyotropic liquid crystalline state of biological assemblies relative to the crystalline state, due to the so-called chiral bilayer effect, which will be discussed in more detail in Section 4.2. For example, 10-nonacosanol, extruded from the lipophilic wax layer of pine needles, forms fluid lipid tubules rather than crystals. Although it is difficult to establish the enantiopurity of the natural product, the fact that synthetic pure enantiomers produce tubules while the racemate gives platelets suggests that the biologically relevant morphology is attained because of the enantiopurity of the biomolecule. °... 

Surfactant molecules are amphiphilic and associate together in aqueous solution to form various structures micelles, microemulsions, vesicles, lyotropic liquid crystalline phases. In each case, their alkyl chains group together and their polar heads form a layer which separates them from the water. The laws governing this self-assembly involve subtle combinations of the two principles, order and mobility. Some fascinating illustrations are provided by the cell membrane in biological systems. In this case, order and mobility are related to the structure of functional units made up of lipids and proteins [6.10]. Such examples could only encourage chemists to carry out novel syntheses which would produce molecules capable of self-assembly. 

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