Switching dynamics and surface forces in thresholdless “V-shaped” switching ferroelectric liquid crystals

The electrostatic model of thresholdless V-shaped switching is able to explain the general low frequency (quasistatic) electro-optic behavior of smectic-C* ferroelectric liquid crystals (vFLCs). Here, dynamical equations based on the electrostatic model are developed which predict a vFLC cell’s small-amplitude switching speed and which also show that a strongly amplitude-dependent switching speed is expected. A relationship between the switching time constants of analog vFLCs and of the faster, yet structurally similar, binary FLCs is found. The electrostatic model applies in the limit where the FLC’s spontaneous polarization is large enough to completely overwhelm surface and elastic forces. This analysis suggests that, in many cases of practical interest, electrostatic energies may be low enough for surface forces to play an important role even when the director structure is strongly stiffened by a large polarization charge. It is shown that the addition of surface forces to the electrostatic model can improve agreement between the model and the observed dynamical response of vFLC cells.