Figure 2.

Schematic arrangement of rod-shaped molecules in typical thermotropic liquid-crystalline mesophases. a) Nematic phase. The average molecular orientation is signified by the dark arrow running along the long molecular axis, namely the director $\widehat{n}.$ b) Smectic A phase. The director is oriented parallel to the layer normal (here the z axis represented by the blue arrow). Within the layers the molecules are isotropically distributed. c) Smectic C phase. The director is tilted with respect to the layer normal (blue arrow). Within the layers the molecules are isotropically distributed. d) Chiral nematic phase. Here, the pitch is drawn orders of magnitude smaller than in reality. e) Chiral smectic C phase. The sketch to the left depicts in a simplistic way the chiral twist of the director along the helix axis. f) Columnar phase comprised of disc-shaped molecules stacking their cores on top of each other in a hexagonal arrangement.