Synthesis and Electro-Optical Properties of Some Ferroelectric Liquid Crystals Derived from Lactic Acid

Abstract

We have synthesized two series of liquid crystals, viz. 4′-(ω-(2-ethoxy) propoxy)alkoxyphenyl 4-alkoxybenzoate, 2, (abbreviated C_m-C_n-OEt*) and 4′-(ω-(2-chloro)propoxy)alkoxyphenyl 4-alkoxybenzoate, 3, (abbreviated C_m-C_n-Cl*). Compounds belonging to the latter mainly exhibit smectic A and B phases while the former show enantiotropic smectic C* at or near room temperature as well as A and smectic phases of higher order. The magnitude of the spontaneous polarization is moderate (–4 nC/cm²). There is no alteration in sign for the spontaneous polarization and for the helical pitch as function of the n value. The C_m-C₃-OEt* and C_m-C₅-OEt* compounds are exhibiting unusually long helical periodicity for a pure compound (30–50 μm). Compounds of series 2 also show a close relationship between spontaneous polarization and tilt angle giving a practically temperature independent ratio P/θ, making the definition of a material constant P_o = P/θ meaningful.