Mesomorphic properties and structure of compounds on isophtalic acid base

Our investigation purpose is the determination of the molecular structure peculiarity of banana-shaped compounds, which promotes the formation "banana" phase or prevents from it. The homologous series of the 4-methoxy-1,3-benzene-dicarbonic acid esters have been synthesized and their mesogenic properties have been studied. On the basis of the polarization microscope it is shown that compounds containing 5,6 or 12 carbon atoms in the lateral alkyl chain are non-mesomorphic. But compounds with 7 - 9 carbonic atoms in the lateral alkyl chain form smectic phase. On the base of differential scanning calorimeter measurement and X-ray diffraction investigation this phase may be preliminary attributed to "banana"-smectic phase, we kind of which we have not identified.