Symmetries and physical properties of polar columnar phases in materials composed of achiral molecules

Motivated by puzzling experimental observations made in compounds composed of banana-shaped molecules, we investigate the symmetries and the physical properties of liquid crystalline columnar phases with a macroscopic polarization in achiral materials. This study is driven by two key observations made for the still poorly understood B7 phase: a) freely suspended films decompose spontaneously into strands and b) several of the textures observed for the B7 phase are reminiscent of textures observed for liquid crystalline columnar phases. One of the main results of our analysis is that a chiral phase of C-1-symmetry results as soon as the macroscopic polarization includes an angle different from zero or 90degrees with the columnar axes. We argue that a chiral columnar phase composed of achiral molecules, not previously considered for classic columnar phases, is sufficient to account for many of the unusual physical properties of B7.