Columnar and interdigitated structures from apolar discotic mesogens with radial dipoles. A Monte Carlo study

We have simulated, using a Monte Carlo method, a system of apolar Gay–Berne discotic particles without dipoles and with two or three dipoles symmetrically embedded in the disc. The dipoleless system can form nematic and hexagonal columnar mesophases. Adding two inplane antiparallel radial dipoles has the effect of destabilizing the columnar ordering, in favour of a fully interdigitated arrangement of the molecular stacks, with strong correlations in the plane perpendicular to the director and large biaxiality. No columnar phase is observed for the systems with three planar radial dipoles with threefold symmetry up to very low temperatures. Finally, on decreasing the strength of the three dipoles, a columnar noninterdigitated phase is observed.