Direct confirmation of biaxiality in a bent-core mesogen through the measurement of electro-optic characteristics

We propose a method to confirm the biaxial phase in thermotropic nematic liquid crystals from measurement of the electro-optic characteristics. The electro-optic transmittance curve shows monotonic decrease to zero in the uniaxial phase but the curve shows a U-shaped behavior (or a monotonic decrease to nonzero transmittance) in the biaxial phase. In a bent-core mesogen 4,4'(1,3,4oxadiazole2,5diyl)dipheptylbenzoate (ODBP-Ph-C-7), known to be in the nematic phase at temperatures between 173 and 222 degrees C, it has been found that its electro-optic curve at 190 degrees C shows a U-shaped behavior, while the curve at 210 degrees C shows a monotonic decrease to zero transmittance. We believe that these experimental results confirm the biaxial nature of ODBP-Ph-C-7. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3108486]