Synthesis and Mesomorphic Characterization of Azoketones

Abstract

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 by n-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 C2 to C4 homologue; smectic A phase emerges from the C4 derivative in the monotopic form, which becomes enantiotropic in the C5 homologue and persists till the last C16 derivative studied. The esterified series (II) namely: 4-(4′-n-alkoxy benzoyloxy) phenyl azo 4″-propiophenones shows only nematic phase in C1 and C2 homologues. The smectic phase emerges from C3 derivative, together with nematic phase and the series exhibits polymesomorphism from C3 to C12 homologue. 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.