The influence of lateral apolar substituents on the mesomorphic behaviour of tetracatenar liquid crystals

Several series of new tetracatenar mesogens consisting of a five-ring aromatic core and bearing one or more apolar lateral substituents in the central benzene ring of the molecule have been synthesized and their mesomorphism is characterized by polarization microscopy, differential scanning calorimetry, and X-ray diffraction methods. Introduction of one, two, or four methyl groups into these tetracatenar mesogens destabilized columnar organization typical of the long-chain homologs, but did not suppress smectic C and nematic phases. Introduction of larger substituents did, however, suppress lamellar organization (C₁₅H₃₁) or mesomorphism (tert-butyl) totally.