Amphotropic liquid crystals

The liquid crystalline state is a fundamental organization of matter, which combines order and mobility on a molecular, supramolecular and macroscopic level. In many cases the molecules can show both thermotropic and lyotropic liquid-crystalline (LC) phases, which is described as amphotropic behavior. Block-copolymers, polyhydroxy amphiphiles, disc-like, rod-like, polycatenar and banana-shaped LC molecules are discussed with respect to their amphotropic behavior with specific and non-specific solvents. The interactions of salts with polyether chains, leading to halotropic mesophases, and the interaction of aromatic electron acceptor molecules with electron-rich aromatic molecular parts are discussed in relation to lyotropic mesomorphism induced by classical solvent molecules. Polyphilic amphotropic materials showing more complex mesophase morphology and amphiphiles showing a hierarchical order of different levels of order are pointed out as future directions.