Abstract: A series of novel 4-(4'-alkoxybiphenyl-4-carboxy)benzaldehyde was synthesized via Einhorn raction by using 4-hydroxybenzaldehyde and p-alkoxybiphenylyl carbonyl chloride as the raw materials. The compounds were identified by using elemental analysis, infrared spectrum, nuclear magnetic resonance, and mass spectrometry. The liquid-crystalline behavior of the compounds was characterized by differential scanning calorimetery(DSC), polarizing optical microscopy(POM), and polarimetric analysis. It was found that all the compounds went into liquid crystal phase over the T_m. The typical chiral smectic Cphase or smectic phase or cholesteric phase, and nemetic phase texture can be observed. In this study, we found that the rotation was maintained during the synthesis process and all the chiral compounds were optically highly active. Both melting point(T_m) and isotropization temperature(T_i) except those of compounds 2a and 4a change regularly with the carbon numbers of the end alkoxy increased. There is a gradual increase in smectic phase length and in the smectic-nemetic transition temperature. At the same time there is a gradual decrease in nemetic phase length until in the dodecyl, purely smectic properties are encountered.

Key words: Aromatic aldehyde compound, Liquid crystal phase, Thermotropic liquid clystal