Biaxial molecular arrangement of rod-disc molecule under an electric field

The biaxial molecular orientation of nematic liquid crystal (NLC) was investigated. An electro-optic LC cell filled with RD12 molecules was synthesized using sealed indium thin oxide (ITO) glass. A PZD350 Trek DC voltage generator was connected to the ITO junctions to apply an electric field across the electro-optic LC cell. The cell was first heated to the I melt of RD12, and gradually cooled to 125°C. The molecular orientation of the NLC phase was characterized using 2D wide angle x ray diffraction (WAXD). The sample prepared by quenching the cell into a dry ice/acetone mixture with the 150 V electric field, was subjected to two different incident X-ray beams. It was observed that the material exhibited nematic phase between 121 and 130°C. Result shows that the long axis of the cyanobiphenyl rods are in-plane with the triphenyl discotic cores and the optical directors of the mesogens are orthogonal to each other, creating a biaxial N phase.