Mesophase behavior of new linear supramolecular hydrogen-bonding complexes.

Thermal and mesophase behavior of four new series of hydrogen-bonded supramolecular complexes (I/II) were investigated by differential scanning calorimetry and phases identified by polarized light microscopy. All hydrogen-bonded complexes formed from 4-alkoxyphenylazobenzoic acid (I) and 4-(4'-pyridylazophenyl)-4''-alkoxybenzoates (II). The results revealed that the prepared complexes are dimorphic, possessing smectic C and nematic phases. The comparison, made between the present series and previously investigated simpler, I/III and angular, I/IV analogues, revealed that increasing the length of the mesogenic core and/or linearity of complex increase the stabilities of both the smectic C and nematic phases.