Abstract

A new homologous series of Schiff base esters comprising a terminal iodo substituent was studied. The iodo substituent contributes to the molecular polarizability, thus, affecting intermolecular interactions, hence, resulting in smectic polymorphism. The mesomorphic properties were studied using differential scanning calorimeter (DSC) and polarizing optical microscope (POM). Whilst the lower members, n-ethanoyloxy, n-propanoyloxy, n-butanoyloxy and n-pentanoyloxy derivatives were non-mesogens, enantiotropic smectogenic A phase was observed in the medium members (n-hexyloxy and n-heptanoyloxy derivatives). Further lengthening of the alkyl chain from C8 to C18 members saw the induction of new phase which was identified as smectic B phase under microscope. The homologous members were compared with structurally related series to establish their chemical structure-mesomorphic behavior relationships.

Key words: 4-{[(4-iodophenyl) imino] methyl} phenyl alkanoate, thermotropic properties, smectic A, smectic B, polarizability.

Abbreviation

DSC, Differential scanning calorimeter; POM, polarizing optical microscope; MBBA, N-(4-Methoxybenzylidene)-4-butylaniline; EI-MS, electron ionization mass spectrum; NMR, nuclear magnetic resonance; TMS,trimethylsilane; DMF, dimethylformamide; DMAP, dimethylaminopyridine UV,ultraviolet; IR, Infrared; FTIR, fourier transform infrared.