Molecular theory of ferroelectric ordering in bent-core smectic liquid crystals

Abstract:

Antiferro- and ferro-electric ordering is observed in orthogonal smectic phases composed of nonchiral bent-core molecules. These systems are the only proper fluid ferroelectrics confirmed experimentally so far. The delicate balance between the tendencies for local parallel and antiparallel ordering of molecular electric and steric dipoles is analysed and a conclusion is made that it is strongly shifted in favour of ferroelectric ordering in restricted geometries. This is a reason why dipolar ordering is more likely to occur within a smectic layer. We derive model interaction potentials for polar bent-core molecules and present the results of the mean-field theory of ferroelectric ordering in the orthogonal smectic phase taking into account also the molecular biaxiality.