Unusual Smectic-A Layering in a Homologous Series of Isothiocyanato Compounds

Abstract

The smectic-A (SmA) phases exhibited by several homologs belonging to the newly synthesized 4-isothiocyanatophenyl-4′-n-alkyloxybenzoate series (n.O.NCS) show unusual features. Although the X-ray studies show that the layer thickness/molecular length ratio (dll) of the lower homologs is less than 1 indicating a monolayer packing, dielectric studies reveal the existence of strong antiparallel correlations near the isotropic-SmA phase transition, a feature that has hitherto not been observed for any polar monolayer SmA phase. Miscibility studies prove that the SmA phase of these materials is miscible with both the monolayer (SmA₁) and the partial bilayer (SmA_d) phases.