Polarization In Ferroelectric Liquid Crystals Research Articles

Contributions of the molecular species to the magnitude of the spontaneous polarization in ferroelectric liquid crystals

Abstract In certain ferroelectric liquid crystals that contain the biphenylyl moiety, the spontaneous polarization undergoes a change in direction relative to the optical axis of the system as a function of temperature. Consequently, at a characteristic temperature for a particular derivative, the polarization vanishes. A model based on the presence of at least two species, interconvertible via an activation barrier is proposed to explain this extraordinary behaviour of the polarization. It is suggested that these species are most likely identified with the rotational conformers of these materials while they are in their liquid-crystalline states.

Helicoidal Structure and Spontaneous Polarization in the Mixtures of Ferroelectric Liquid Crystal with Its Racemate

Some phenomena that critically depend on the helicoidal pitch and spontaneous polarization in ferroelectric liquid crystals are studied. These quantities are changed by mixing active DOBAMBC with its racemate. The phenomena investigated are: (1) Directions of the spontaneous polarization at the bounding surfaces, (2) Critical thickness for realizing bistability, (3) Two types of fringe patterns corresponding to the helicoidal pitch, (4) Disclination lines in the middle of a cell, (5) Unwinding of the helicoidal structure induced by an electric field, and (6) Winding of the helicoidal structure near the phase transition to Sm A.

Flexo- and piezo-electric terms in the spontaneous polarization of ferroelectric liquid crystals

Abstract The independent measurements of the depth of the electro-optical modulation, pyro-electric coefficient and pitch of the helix were carried out for mixtures of ferroelectric liquid crystals DOMBAMBC and HOBACPC with different signs of chirality. The flexo- and piezo-contributions to the total value of the spontaneous polarization were calculated from experimental data. It was shown that the piezo-electric polarization dominates in the “classical” ferroelectric liquid crystals.

Tempearture Dependence of Tilt, Pitch and Polarization in Ferroelectric Liquid crystals

We persent tempeature measurements of the importnt parameter defming the properties of the semctic C* Phase in a series of schiff bases. The pitch of the helica texture is measured optically. The m...