Page "Liquid crystal" Paragraph 79

The ability of the director to align along an external field is caused by the electric nature of the molecules.

Permanent electric dipoles result when one end of a molecule has a net positive charge while the other end has a net negative charge.

When an external electric field is applied to the liquid crystal, the dipole molecules tend to orient themselves along the direction of the field.

( In the following diagram, the black arrows represent the electric field vector and the red arrows show the electric force on the molecule.