Mesogen

[2] The liquid crystal properties arise because mesogenic compounds are composed of rigid and flexible parts, which help characterize the order and mobility of its structure.

The nematic phase (N) is the least ordered and most fluid liquid crystalline state or mesophase that is based on the rigid core of mesogen moieties.

[3] Discotic mesogens contain a disk-shaped rigid core and tend to organize in columns, forming columnar liquid crystal phases (Col) of long range positional order.

[2] Calamitic mesogens contain a rod-shaped rigid core and tend to organize in distinctive layers, forming lamellar or smectic liquid crystal phases (Sm) of long range positional order.

[3] The rigid units of these phases pack in a way so that the highest density and polar order are achieved, typically with the apex of the bent rod pointing in one direction.