ANOMALOUS ELECTROCLINIC EFFECT ASSOCIATED WITH MOLECULAR-CONFORMATION DISTRIBUTIONS IN CHIRAL SMECTIC-A LIQUID-CRYSTALS

We show that for some chiral compounds the field-induced molecular tilt in the smectic-A phase undergoes a peculiar sign inversion with respect to the layer normal as temperature increases. The electroclinic response of the system to an external electric field completely disappears at a characteristic temperature. This unusual behavior can be described in terms of a dynamically fluctuating mixture of at least two conformers that are separated by an energy barrier in their liquid-crystalline states. It is found that the energy barrier between these two conformers is comparable to the rotational barrier in normal hydrocarbons.