Pre-organized liquid crystals: biaxial nature of laterally-connected dimer

Biaxial nematic liquid crystals have attracted much attention from both fundamental and application points of view, because the fast response based on the rotation of the minor director is expected. So far, different molecular designs have been proposed for the emergence of the biaxial nematic phase. Among that, we have been interested in applying "preorganization" concept on generating the biaxiality. Dimeric liquid crystal compounds have been prepared in line with this concept in which two mesogenic parts are linked by the biphenyl connecting group. The pre-organized dimmer shows an anomalous textural change, for vertically-aligned and free-standing film samples, at the smectic C (SmC)- nematic (N) phase transition, in which the Schlieren texture of the SmC changes into the other Schlieren texture of the N phase. There are two possible explanations for this textural change, i.e., the occurrence of the director change at the SmC-N phase transition or the emergence of biaxiality in the N phase. The electric-field-induced birefringence has also been measured in detail for investigating the biaxial nature of the sample.