High nematic ordering in a bent-core smectogen showing a biaxial nematic phase: A 13C NMR study

Carbon-13 NMR spectroscopy has been used to probe the orientational ordering of a bent-core liquid crystal A131. Both the carbon chemical shift tensors in a rotating solid sample and chemical shifts from the aligned mesophases were determined. These results allow us to probe the local order parameters of the five phenyl rings in the liquid crystalline molecule. It is found that the conformation and ordering of the bent-shaped core significantly change between the uniaxial and biaxial nematic phases, with the highest local nematic order not associated to the central ring in this azo substituted bent-core mesogen.