The search for thermotropic biaxial nematics

A molecular field approach is used to predict phase transitions to biaxial nematics, by taking into account the existence of conformational equilibria for the mesogenic molecules and the specific biaxiality of the conformers. A shape model is used to relate the molecular structure to the biaxiality parameters entering the theory. It is shown that interconversion processes between conformers make the conditions for biaxial phases to exist less critical. However, the design of compounds with molecular biaxiality sufficiently large to sustain a biaxial nematic phase still appears a challenging task.