Mesomorphic properties and molecular structure. I. Structure of the smectic A phase in the 4-acetyl-4′-n-alkanoyloxy-azo-benzene series

This paper reports an investigation by dilatometry and x-ray diffraction of the structure at the molecular level of the smectic A phases occuring in homologous series of liquid crystals, namely the 4-acetyl-4′-n alkanoyloxyazobenzene series. First, several structural parameters referring to the aromatic part and to the paraffinic chain were obtained; then, on the basis of these parameters, a model was proposed concerning the structural organization of the molecules inside the smectic A layers. According to this model, a bilayer organization of the molecules was found to occur with a strong segregation between paraffinic and polar parts of the molecules, along with a pronounced spreading of the aliphatic chains at the interface.