Randomly polarised smectic A phase exhibited by bent-core molecules: experimental and theoretical studies

Abstract

We report experimental studies on a newly synthesised bent-core liquid crystal exhibiting partial bilayer SmAdPR and SmAdPA phases. Though the SmAdPR phase appears to be optically uniaxial as that of the SmA phase, the observed distinctive properties of the SmAdPR phase are (a) a current peak associated with a polarisation reorientation process under the application of a triangular wave voltage, (b) large variation of the effective birefringence of the planarly oriented sample with the applied in-plane electric field and (c) the presence of a strong dielectric mode. We have developed a simple theoretical model to describe the observed properties of the SmAPR phase and the transition from the SmAPR to the SmAPA phase. We propose that the above characteristic properties of the SmAPR phase arise due to the strong coupling between the transverse polarisation and the transverse polar order of the bend directions of the bent-core molecules in the layers.