Symmetries and physical properties of polar columnar phases in materials composed of achiral molecules
Theoretische Physik III, Universität Bayreuth - 95440 Bayreuth, Germany
2 Advanced Liquid Crystal Technologies - P.O. Box 1314, Summit, NJ 07902, USA
3 Max-Planck-Institute for Polymer Research - P.O. Box 3148, 55021 Mainz, Germany
Accepted: 12 November 2001
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 C1-symmetry results as soon as the macroscopic polarization includes an angle different from zero or 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.
PACS: 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order / 64.70.Md – Transitions in liquid crystals / 05.70.Ln – Nonequilibrium and irreversible thermodynamics
© EDP Sciences, 2002