Mesogenic properties and the effect of 1,2,4-trisubstitution on the central benzene nucleus of a three-ring mesogen

Four mesogenic homologous series have been synthesized by fixing a rigid 4- substituted phenylazo group to a resorcinol moiety. In series I and II. one phenolic OH group is esterified by 4-n-alkoxybenzoyl groups: in series III and IV both the phenolic OH groups are esterified by 4-n-alkoxybenzoyl gro ups. All the homologues of series III and IV exhibit low melting smectic C phases. Monoesters of series I and III having free lateral hydroxy group wi th strong hydrogen bonding, exhibit high temperature nematic phases. The ef fect of different substituents on mesomorphic properties is discussed. One homologue of series III was doped with a chiral dopant and its spontaneous polarization evaluated.