Prediction of flow-aligning and tumbling in a bent-core nematic liquid crystal using measurements of orienation order parameters

The flow behavior of bent-core nematic liquid crystal (A131), which has been known to exhibit a biaxial nematic phase, is predicted by measurements of 2$^{nd}$ and 4$^{th}$ rank orientation order parameters. Using experimentally determined uniaxial, $<$P$_{200}>$ and $<$P$_{400}>$ , and biaxial orientation order parameters, $<$P$_{220}>$, $<$P$_{420}>$ and $<$P$_{440}>$ from polarized micro-Raman spectroscopy, we compute the tumbling parameter, $\lambda $. The relationships between the order parameters and tumbling parameter derived by 2 different groups are used and the results are computed: a molecular theory by Archer and Larson (1995), that by Kroger and Seller (1995) for uniaxial system, and Leslie's theory for 2-director continuum. Temperature evolution of tumbling parameter shows the transition from a flow alignment regime to a tumbling instability. The results of the temperature evolution of tumbling parameter of bent-core nematic LC are compared to those of pure nematic LC (5CB) and LC mixture (E7).