Mesogenic cinnamates with a substituted ethyl terminal chain

Two new mesogenic homologous series of liquid crystalline cinnamates with substituted ethyl tails, beta-methoxyethyl [4-(4'-n-alkoxycinnamoyloxy)benzoates (I) and beta-chloroethyl [4-(4'-n-alkoxycinnamoyloxy) benzoates (II), have been synthesized and characterized by a combination of elemental analysis and standard spectroscopic methods. In series I, lower-chain members exhibit nematic mesophase, middle members exhibit enantiotropic nematic as well as smectic A (SmA) mesophases, whereas higher members exhibit only an enantiotropic SmA mesophase. In series II, methoxy to n-butyloxy derivatives exhibit a monotropic nematic mesophase. The SmA mesophase commences from n-propyloxy derivative as monotropic and persists up to the last member synthesized. The mesomorphic properties of present series were compared with each other and with a structurally related mesogenic homologous series to evaluate the effects of substituted ethyl tail and cinnamoyloxy central linkage on mesomorphism.