Various columnar phases formed by bent-core mesogens

Two new compounds containing bent-core mesogens are presented in which a flexible central methyleneoxycarbonyl unit acts as the bent fragment. The compounds form different two-dimensional columnar ('B-1') phases both with a rectangular lattice but different in the angle of the director of the molecules with respect to the a-axis of the lattice. Based on X-ray diffraction measurements structural models are proposed which cannot be described with the common model of p2mg symmetry for B-1 phases of bent-shaped molecules. The new models are of layer group symmetry (p11n and pm2(1)n) and are discussed as a new common model for two-dimensional columnar phases of bent-shaped mesogens.