Mesophase stability of new Schiff base ester liquid crystals with different polar substituents

Four new groups of Schiff base ester liquid crystal compounds, 4-((4'-substituted phenylimino) methyl)phenyl-4-alkoxybenzoates, Ina-d, were prepared and investigated for their mesophase formation and stability. Each group constitutes four homologous series that differ from each other by the polar substituent X (CH3O, CH3, H, and Cl). Within each homologous series, the number (n) of carbons in the alkoxy chain varies between 6, 8, 10, and 12. Molecular structures of the prepared compounds were confirmed via FT-IR, H-1 NMR, mass spectroscopy, and elemental analysis. The mesomorphic properties were investigated by differential scanning calorimetry and polarised light microscopy. Comparative studies between the present series and previously investigated 4-(4-substituted phenylazo)phenyl 4-alkoxybenzoates revealed that the phenylimino mesogenic core increases the mesophase stability rather than the azo analogues. [GRAPHICS] .