We have synthesized liquid crystal (LC) mesogens based on a nonlinear oxadiazole unit that exhibit nematic phases near 200 °C. Polarized microscopy and conoscopy indicate that these LCs are biaxial nematics. Unambiguous and quantitative evidence for biaxiality is achieved using 2H NMR spectroscopy. “2D powder” spectra, obtained by rotating 2H-labeled samples about an axis perpendicular to the magnetic field at ∼200 Hz, yield phase biaxiality parameters of ∼0.1 when coupled with rigorous and proven simulations.
Physical Review Letters
- Pub Date:
- April 2004
- Orientational order of liquid crystals;
- electric and magnetic field effects on order;
- Experimental determinations of smectic nematic cholesteric and other structures