Origin of tilted-phase generation in systems of ellipsoidal molecules with dipolar interactions

Abstract

We report Monte Carlo simulation studies of tilted smectic liquid crystal phases exhibited by systems of rodlike molecules having permanent dipole moments. For a theoretical understanding of the microscopic origin of the tilted smectic phases, different systems consisting of prolate ellipsoidal molecules of three different lengths, embedded with two symmetrically placed terminal antiparallel dipoles, are investigated. We find that the presence of a stable tilted phase depends crucially on the molecular elongation, which effectively makes the dipolar separation longer. We observe that in the case of molecules with transverse dipoles the tilt angle in the smectic phase gradually increases from zero to a large magnitude as we increase the molecular length, whereas systems with longitudinal dipoles show small tilts over different elongations. In this work we determine the combined contribution of dipolar separation and transverse orientations in generating biaxial liquid crystal phases with large tilt angles.