Study of the mesomorphism of benzoates and cinnamates

Two ester homologous series of carboxy (-COO-) and ethylene-carboxy (-CH=CH-COO-) mesogens, viz. α-4-[4’-n-alkoxybenzoyloxy] phenyl β-4’’-methoxy benzoyl ethylenes (1) and α-4-[4’-n-alkoxy cinnamoyloxy phenyl β-4’’-methoxy benzoyl ethylenes (2)] are discussed. Series (1) and (2) differ at their central linking group. Mesophase are observed at four and five number members in both homologue series. Enantiotropic nematogenic property is observed in both series (1) and (2), while some smectic property is exhibited in series (2). Thermal stability of nematic-isotropic in series (1) is relatively low as compared to (2), smectogenic property is totally absent in series (2). In phase diagram, solid-nematic, solid-isotropic, and nematic-isotropic curve follow zigzag path rising and falling. Transition temperatures are observed through hot stage polarizing microscope. Analytical data supports the structure of molecules. Threaded, Schlieren-type textures of homologues are observed through microscope.