The first antiferroelectric liquid crystal (AFLC) exhibiting a (chiral) nematic phase, a
combination which has long been the goal of synthetic chemists working with polar liquid
crystals but which at the same time represents a fundamental contradiction in terms of
translational order, was recently reported by Nishiyama and co-workers. We have investigated this chiral twin dimer by optic, electrooptic, and dielectric methods and conclude that
it is not an ordinary AFLC material, but one where the peculiar properties of bent-core
smectics are combined with those of ordinary rod-shaped liquid crystals. The compound
exhibits a new type of nematic−smectic phase transition, connected with a change of molecule
conformation from rod- to bent-shaped. This also has an important impact on the chiral
interactions in the system. Toward the high-temperature end of the smectic phase, the energy
balance between bent conformation smectic and straight conformation nematic can be shifted
by an electric field such that the transition to the nematic phase with stretched-out molecules
can be field-induced.