Electro-optic characteristics of de Vries tilted smectic liquid crystals: Analog behavior in the smectic A* and smectic C* phases

Abstract

Chiral smectic A liquid crystal materials of the de Vries type (with molecules tilted relative to the layer normal) exhibit analog field-induced (electroclinic) optic axis rotation accompanied by an increase in birefringence. We identify two such de Vries smectic A* materials and use them to develop and test models for these characteristic electro-optic effects. These materials also exhibit colossal analog field-induced optic axis rotation in the lower temperature smectic C* phase, a consequence of polarization charge stabilization, and of polarization screening of the applied field in the liquid crystal.

Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

“…Besides the excellent, stable chemical structure, the electroclinic effect of the SmA * LC offers the additional benefit of a faster response than the ferroelectric LC and the grayscale adjustment capability [82]. The rapid tilt angle conversion also enables a wide range of applications in display technology [83]. In addition, after fabricating SmA * LC and using it to fill an LC cell with no polymer alignment film, we observed a complete vertical alignment of LC molecules (homeotropic texture) under crossed polarizers [78].…”

Chiral smectic-Aand smectic-Cphases with de Vries characteristics

“…This model was used by Clark et al [29] to explain the electro-optical properties of de Vries materials C4 and C6. This model assumes that in the absence of an electric field in the Sm-A * phase at a fixed temperature, the molecules are tilted with a fixed tilt angle and are azimuthally distributed randomly on a cone so that cos ϕ = 0.…”

de Vries behavior of the electroclinic effect in the smectic-A∗phase near a biaxiality-induced smectic-A∗–smectic-<

“…in Ref. [11]) as "superlinear growth". For sufficiently small temperatures the response curve is S shaped (i.e.…”

“…Refs. [6,11]) that has analyzed the change in birefringence as a function of tilt, it is the absolute change rather than the fractional change of briefringence that is considered. In our theory this corresponds to the absolute change in orientational order ∆M (E) = M − M E=0 which is given by:…”

“…The first [6,11,13,14] is to use a Langevin Curve (i) shows the response for T > T c , a critical temperature. In this case the response is continuous but "superlinear", corresponding to positive curvature at small fields followed by negative curvature at large fields.…”