Ester homologous series of mesogens of cis configuration viz. n-Hexyl-p-(-p/-n-alkoxy cinnamoyloxy) cinnamates is synthesized and studied to understand and establish the relation between the molecular structure and mesogenic properties. Twelve homologues are synthesized. Methyl and ethyl derivatives of homologues are nonmesogenic while, n-propyl to n-octyl, n-decyl, n-dodecyl, n-tetradecyl and nhexadecyl derivatives of the homologues are enantiotropically nematogenic in nature. Enantiotropic smectogenic character commences from heptyloxy derivative and end to tetradecyl homologue. Smectic mesophase is absent in hexadecyloxy homologue. Transition temperatures and melting temperatures of homologues are observed through hot stage polarizing microscope. A phase diagram obtained from transition temperatures of homologues. The solid-isotropic/ mesomorphic transition curve adopt a zigzag path of rising and falling tendency in normal manner. Smectic-nematic transition curve rises from nheptyloxy homologue and exhibit falling tendency up to tetradecyloxy homologue and behaves in normal manner without odd-even effect. Nematic-isotropic transition curve initially rises from propyloxy homologue and passes through a maxima at the octyloxy homologue and then smoothly falls to the hexadecyl homologue with exhibition of odd-even effect. Thus nematic-isotropic transition curve behaves in usual manner. The texture of the nematic mesophase is of focal conic fan or batonnate shaped. Analytical data support the molecular structure of homologues. Thus, series is predominantly nematogenic and partly smectogenic in enantiotropic manner.
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