Two mesogenic homologous series are synthesised, by fixing a rigid 4′-propiophenone group to 4-Hydroxy phenyl azo moiety. The hydroxy group is etherified and esterified byn-alkyl chains and 4-n-alkoxy benzoyl groups respectively. The etherified series (I)viz:4-n-alkoxy phenyl azo 4′-propiophenones exhibit nematic phase from C2to C4homologue; smectic A phase emerges from the C4derivative in the monotopic form, which becomes enantiotropic in the C5homologue and persists till the last C16derivative studied. The esterified series (II) namely: 4-(4′-n-alkoxy benzoyloxy) phenyl azo 4″-propiophenones shows only nematic phase in C1and C2homologues. The smectic phase emerges from C3derivative, together with nematic phase and the series exhibits polymesomorphism from C3to C12homologue. The last two homologous exhibit only smectic A phase. Both the homologous series are thermally very stable and exhibit a wide mesomorphic range. Their thermal stabilities and other characteristics are discussed.