Synthesis and Mesomorphic Properties of a Novel Ester Homologous Series: 4-(4′-n-Alkoxy Benzoyloxy) Benzyl Cinnamates

Abstract

A novel homologous series 4-(4′-n-alkoxy benzoyloxy) benzyl cinnamates was synthesized and studied with a view to understanding and establishing the relationships between mesomorphism and molecular structure. The novel series consists of eleven members with the commencement of mesomorphism from the pentyloxy homologue onwards to the hexadecyl homologue. The remaining homologues are nonmesomorphic. All the mesomorphic homologues exhibit smectogenic mesomorphism in addition to nematogenic mesomorphism for a definite temperature range in an enantiotropic manner, except for the pentyloxy homologue, which exhibits only a nematogenic mesophase in an enantiotropic manner without the formation of a smectic phase. The texture of the nematic mesophase is of the threaded or Schlieren type and the smectic mesophase is of the type A or C texture, as determined by a miscibility method. Transition temperatures were observed through an optical polarizing microscope equipped with a heating stage. The transition curves of a phase diagram predominantly behave in a normal manner, but partly deviated from normal behavior with the exhibition of an odd–even effect. Analytical and spectral data confirms the molecular structures of all homologues. The mesomorphic behavior of the present series is compared with other structurally similar known series. The mesomorphic temperatures vary between 106°C and 180°C. The mesophase length varies between 33°C to 53°C. Thus, the novel series is predominantly nematogenic and partly smectogenic with relatively high transition temperatures and is of a high melting type. The average thermal stabilities for smectic and nematic phases are 144.1°C and 171.4°C, respectively.