Occurrence of the Smectic C phase for 3-(2-hydroxy-4-Alkoxybenzylidene-amino)dibenzofurans

The title compounds were investigated on the occurence of the smectic C phase. Comparison with the geometrical analogues, 3-(2-hydroxy-4-alkoxybenzylideneamino) dibenzothiophenes and 2-(2-hydroxy-4-alkoxybenzylideneamino)fluorenes, indicated that a molecular symmetry favoring the occurrence of the smectic C phase is not always required if the molecule has an appropriate magnitude of the transverse dipole, and that the thermal stability of the smectic C phase (smectic C to smectic C to smectic A and to nematic phase transition temperatures) of these compounds rises with the increase of the magnitude of transverse dipole moments.