Four different classes of nonconventional liquid crystals with perfluorinated chains were synthesized: polyhydroxy amphiphiles, amphiphilic biphenyl derivatives, pentaerythritol tetrabenzonates and bolaamphiphiles with lateral fluorinated chains. All types of mesophases (smectic, columnar, bicontinuous cubic and micellar cubic) were found in the first three classes of these liquid crystals. As for bolaamphiphiles with lateral fluorinated chains, by stepwise enlargement of the volumes of the lateral chains with respect to the length of the rigid cores, a transition between two orthogonal sets of layer structures occurs, namely from the conventional smectic phase in which the calamitic units are organized perpendicular to the layer planes, to nonconventional smectic phase in which the calamitic units are organized parallel to the layer planes. Different columnar phases are found as intermediate phases at the transition between these two layer structures. All the experimental results indicate, that the fluorophobic effect caused by the fluorinated chains can be used in combination with other incompatibilities to increase the micro-segregation of incompatible parts into different regions and can stabilize the mesophase. There are three distinct effects of the fluorinated chains in these systems: i) The fluorinated segments stabilize the mesophases due to the increased incompatibility with both aromatic and polar molecular parts; ii) simultaneously, they reduce the melting points in many cases and thus enlarge the mesomorphic regions; iii) the larger space required by the fluorinated chains increases the size of the segregated lipophilic regions and therefore, modifies the phase structure and leads to novel mesophases. |