Amphitropic mesophases

The structure and function of cell membranes have long been associated with lyotropic liquid crystalline phases. Since most of the glycolipids are amphitropic (both thermotropic and lyotropic) their was an increase of interest in the comparison of the structures of both types of mesophases formed by the same compound. 

This family of noncovalently bonded PLCs may also include polyelectrolyte + surfactant complexes which, as will be seen, can also give rise to liquid crystalline mesophases. In these complexes there is only a flexible alkyl chain attached to the ionic head group in the small molecule constituent, with no rigid aromatic core present. Since surfactants themselves are frequently thermotropic liquid crystals, it is not surprising that their complexes with polyelectrolytes may produce PLCs, in both cases driven by the incompatibility between the ionic and aliphatic parts leading to amphitropic systems [27]. 

Fig. 3 The condensed mesophases formed by the amphitropic liquid crystal octyl p-D-glucopyranoside. The smectic A phase exists from 67 to 106 °C, whereas the lyotropic phases exist at room temperature and as a function of solvation with water.

The terms liquid crystal, mesophase, or mesomorphic state are used synonymously to describe a number of different states of matter in which the molecular order lies between the almost perfect long-range positional or orientational order of solid crystals and the long-range disorder found in ordinary isotropic liquids. Two main classes of liquid crystals are usually distinguished lyotropic and thermotropic. In lyotropic mesophases, the combination of order and mobility can be achieved by using a solvent thermotropic mesophases are based on the temperature-induced mobility of form-anisotropic molecules in the melt. Surfactants can often form both thermotropic and lyotropic liquid crystals i.e., they possess amphitropic properties [2]. 

---