The existence of spontaneous polarization P, in chiral tilted smectic phases was predicted by Meyer twenty years ago[’] and successively confirmed by the measurements in a large variety of different liquid crystalline substances, monomers and polymers, built up of molecules possessing a lateral dipole moment and one or more chiral centers. The spontaneous polarization in these materials is directed along the smectic layers and it is perpendicular to the molecular tilt 8. There is a coupling between P, and 0 which in fact gives a possibility to change the position of the molecules by an applied electric field. However, the presence of helical order of the molecules in the S,, phase, for instance, results in a zero spontaneous polarization. In the surface stabilized ferroelectric liquid crystals (SSFLC) where the helix is completely suppressed, changing the position of the molecules by alternating the direction of the applied electric field results in a substantial electro-optic effect which main features are ultrafast switching, high contrast and bistability.[’]
Ferroelectric and electroclinic properties of the chiral mesogen
SCARAMUZZA, Nicola;
1995-01-01
Abstract
The existence of spontaneous polarization P, in chiral tilted smectic phases was predicted by Meyer twenty years ago[’] and successively confirmed by the measurements in a large variety of different liquid crystalline substances, monomers and polymers, built up of molecules possessing a lateral dipole moment and one or more chiral centers. The spontaneous polarization in these materials is directed along the smectic layers and it is perpendicular to the molecular tilt 8. There is a coupling between P, and 0 which in fact gives a possibility to change the position of the molecules by an applied electric field. However, the presence of helical order of the molecules in the S,, phase, for instance, results in a zero spontaneous polarization. In the surface stabilized ferroelectric liquid crystals (SSFLC) where the helix is completely suppressed, changing the position of the molecules by alternating the direction of the applied electric field results in a substantial electro-optic effect which main features are ultrafast switching, high contrast and bistability.[’]I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.