THE SEARCH FOR THERMOTROPIC BIAXIAL NEMATICS

A molecular field approach is used to predict phase transitions to bia xial 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 structur e to the biaxiality parameters entering the theory. It is shown that i nterconversion processes between conformers make the conditions for bi axial phases to exist less critical. However, the design of compounds with molecular biaxiality sufficiently large to sustain a biaxial nema tic phase still appears a challenging task.