Collective molecular relaxations and electro-optical switching response of a wide room temperature antiferroelectric liquid crystal mixture

Abstract

Antiferroelectric liquid crystals (AFLCs) are advanced smart materials for displays with unique properties of tristate switching. Thermodynamic, dielectric and switching characteristics of a room temperature bicomponent AFLC mixture at eutectic composition was investigated in the present work. The emergence of various phases in the eutectic composition was identified on the basis of observed dielectric relaxation modes and other parameters. Critical electric field (Ec) to unwind the helix, spontaneous polarization (Ps), torsional viscosity (γt) and switching time (ts) have been determined in the ferroelectric (SmC*) and the antiferroelectric (SmCA*) phases from switching experiments. Spontaneous polarization follows the equation, Ps = Po(1-T/Tc)γ in the temperature range of tilted chiral smectic phases, with values of Tc = 91.8 ± 0.1 °C and γ = 0.410 ± 0.005. Value of γ indicates that the SmA* to SmC* transition is of the first order as observed by the enthalpy measurements from the thermodynamic studies. In the AFLC phase of interest, ts is ∼2–3 ms and Ps∼200 nC/cm2. These parameters suggest that the mixture is appropriate base material for electro-optical applications.