Frustrated Smectic Phase Appearing as Transitional State between Single-Layer and Antiferroelectric Bilayer Smectic Phases in Binary Mixtures of Dimeric Compounds

Twin dimers, mOAM5AMOm, form characteristic smectic phases, single-layer SmCAs and antiferroelectric bilayer SmCAb phases. Structural transformation from SmCAs to SmCAb was examined in two series of binary mixtures of 8OAM5AMO8/4OAM5AMO4 and 8OAM5AMO8/16OAM5AMO16. In this transformation, the frustrated SmCAf with density modulation along the layer is formed and the size of modulation increases from 50 to 250 A with variations in mixture contents from an edge near SmCAs to another edge near SmCAb. From polymorphisms shown by some mixtures, it was found that SmCAs and SmCAb are located at high-temperature and low-temperature edges, respectively, and that the SmCAf phase is set between them.