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 SmA_dP_R and SmA_dP_A phases. Though the SmA_dP_R phase appears to be optically uniaxial as that of the SmA phase, the observed distinctive properties of the SmA_dP_R 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 SmAP_R phase and the transition from the SmAP_R to the SmAP_A phase. We propose that the above characteristic properties of the SmAP_R 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.