Effect of methoxy group instead of polar group in the nematic phase of four-ring bent-core liquid crystals

Two achiral four-ring bent-core liquid crystal possessing an alkoxy chain at one end of the molecules and methoxy group at the other end are investigated by using the optical polarizing microscope, electro-optical studies, and dielectric spectroscopy. Both the compounds exhibit enantiotropic nematic phase over a wide range of temperatures. In the dielectric spectroscopic studies of the compounds, only one sharp peak in the loss curve is observed in the entire nematic range. In addition, the dielectric permittivity of the sample is very large. The molecular structures of these two compounds are similar to the compounds studied by Ghosh et al., which are reported to exhibit the ferroelectric-like switching and electro-convection pattern. However, the differences are (a) replacement of the polar halogen substituent at one end of the molecule by a methoxy group and (b) an increased length of the alkyl chain at the other end. These studies confirm the requirement of a polar moiety for the ferro-nematic phase to exist in these four-ring bent-core compounds.