Fig. 1.

Molecular structure of B7 smectic phase and ordering scheme. (A) B7 phase appears upon cooling from the isotropic phase (B) and is formed from the stacking of fluid layers of banana-shaped molecules, where the molecular long axis (n) is tilted (by angle θ) relative to the layer normal (s). In addition, polar order of the molecules leads to a polarization (p), the tilt of the molecular bows in the direction given by tilt direction (c); both are orthogonal to n and s. The polarization is spontaneously splay modulated, producing a periodic array of layer undulations and splay stripes. (C) Structure of the B7 phase of MHOBOW shows the stripe undulation, alternation of polarity and chirality, and two distinct types of defect lines [orange (trough) and brown (elevation) lines].